KR20080028362A - Magnesium Alloy Powder Raw Material, High Strength Magnesium Alloy, Magnesium Alloy Powder Raw Material Manufacturing Method and High Strength Magnesium Alloy Manufacturing Method - Google Patents

Abstract

The Mg alloy powder raw material is made into a relatively small crystal grain size by performing plastic working for compression or shear deformation through a pair of rolls to a starting material powder having a relatively large grain size. The starting raw material powder is Mg alloy powder in which the fine intermetallic compound 21 is deposited and dispersed in the base 22 by heat treatment. In the Mg alloy powder after plastic working, the processing distortion 22 exists in the vicinity of the precipitated intermetallic compound 21. The maximum size of Mg alloy powder after plastic working is 10 mm or less, the minimum size is 0, 1 mm or more, and the maximum grain size of the Mg particle which comprises the base 20 is 20 micrometers or less.

Description

MAGNESIUM-ALLOY POWDER MATERIAL, MAGNESIUM ALLOY WITH HIGH PROOF STRESS, PROCESS FOR PRODUCING RAW MAGNESIUM-ALLOY POWDER MATERIAL, AND PROCESS FOR PRODUCING MAGNESIUM ALLOY WITH HIGH PROOF STRESS}

TECHNICAL FIELD The present invention relates to a magnesium alloy powder raw material, a magnesium alloy produced using the powder raw material, and a method for producing the same, and more particularly, to a magnesium alloy having both high strength and elongation, and a method for producing the same.

Among the industrial metal materials, the lightest magnesium alloy (hereinafter referred to as Mg) alloy is widely used in sports goods, home appliances, aviation and aerospace equipment, and other mechanical parts by utilizing its lightening effect. On the other hand, in order to apply Mg alloy to products and members requiring high reliability, such as automobile parts, further increase in strength is required. In particular, in the design of components, significant improvement in strength is required, and at the same time, it is necessary to realize high elongation (toughness). In other words, by realizing high strength and high elongation, replacement with the aluminum alloy which is a lightweight material of the present state is attained.

In the strength improvement of Mg alloy, it is known that the refinement | fineness of a crystal grain and the dispersion strengthening of a fine intermetallic compound are effective. In particular, a manufacturing method of using Mg alloy powder as a starting material and compacting and solidifying it can form a fine structure as compared with the dissolution and casting method, and it can be said to be a more effective manufacturing process in terms of high strength. Can be.

For example, although the manufacturing method of the high strength Mg alloy using the quick cooling solidification process is proposed, this method is not practical for the following reasons.

(A) High strength can be obtained, but elongation is as low as a few percent.

(B) Since the particle size of the starting material powder is as small as several tens to hundred microns, there are problems of safety in handling, low yield, and economic problems such as cost increase by adding expensive elements. have.

On the other hand, various methods for producing Mg alloys by cutting and solidifying the cutting powder discharged when cutting the Mg alloy material as a starting material are proposed. For example, Japanese Patent Application Laid-Open No. 2-182806 describes a method of extruding after solidifying Mg alloy cutting powder by hot pressing, and Japanese Patent Application Laid-open No. 5-320715 describes molding and extruding Mg alloy cutting powder. Processes are described.

Moreover, in "The manufacturing method of the magnesium alloy member" of Unexamined-Japanese-Patent No. 5-306404, after pressing-molding the aluminum containing Mg alloy powder T6 heat-processed (solvation heat treatment + age heat-processing), the method of extrusion processing focuses on it. It is. In the manufacturing method disclosed herein, when solidifying Mg alloy cutting powder containing an appropriate amount of aluminum (Al), the Mg alloy member excellent in mechanical properties is created by drawing out the effects of both T6 heat treatment and extrusion processing. It is characterized by). The effect of the T6 heat treatment is to uniformly disperse the fine intermetallic compound (Mg ₁₆ Al ₁₂ ) in the holding of the extruded Mg alloy, and the effect of the extrusion processing to refine the crystal grains forming the base of the extruded Mg alloy will be. As a result, for example, Al: 7.8 to 9.2% by weight, manganese (Mn): 0.12 to 0.35% by weight, zinc (Zn): 0.2 to 0.8% by weight, Mg: balance described in the ASTM standard. The Mg alloy obtained by molding and extruding the AZ80 magnesium alloy having a AZ80 magnesium alloy was subjected to T6 heat treatment, and the tensile strength at room temperature was 382 MPa and the elongation was 27%. On the other hand, T6 heat treatment was performed. If not, the tensile strength is reported to be 330MPa, elongation of 15%, showing an effect of improving the tensile strength.

However, in the manufacturing method of the Mg alloy member of Unexamined-Japanese-Patent No. 5-306404, it is reported that the yield strength of an extruded material is 196 Mpa when T6 heat processing is performed, and 200 Mpa when T6 heat processing is not performed, and tension is reported. The improvement effect of the strength is not recognized. This cause is considered as follows. Compared with the crystal grains (50 to 700 µm) of the Mg alloy produced by the conventional dissolution and casting method, recrystallization occurs due to extrusion processing, but the crystal grains are refined, but the size thereof is considered in consideration of the data disclosed so far, It is about 10-20 micrometers. In order to improve the tensile strength, it is necessary to further refine the grains. Based on the start data so far, miniaturization to, for example, 1 to 5 mu m or less is effective for improving the yield strength. Such a Mg alloy having such a fine grain size cannot be realized by only a manufacturing method of pressing and extruding cutting powder subjected to T6 heat treatment.

In addition, a method of further miniaturizing the intermetallic compound (Mg ₁₇ Al ₁₂ ) precipitated and dispersed in the substrate by T6 heat treatment has been proposed, but it is also limited to the level that can be miniaturized by plastic deformation by extrusion processing. In order to improve the yield strength, further refinement of the intermetallic compound and fine and uniform dispersion of the plural intermetallic compounds are required.

An object of the present invention is to provide a magnesium alloy which achieves high strength and elongation and a method of producing the same.

Another object of the present invention is to provide a magnesium alloy powder raw material and a method for producing the same, which are used to manufacture the magnesium alloy.

In the magnesium alloy powder raw material according to the present invention, a relatively small crystal is obtained by performing a plastic working process for compressive or shear deformation through a pair of rolls of a starting material powder having a relatively large grain size. It was made into the particle diameter and is characterized by the following. That is, starting material powder is magnesium alloy powder which precipitates and disperse | distributes a fine intermetallic compound by the heat processing. In the magnesium alloy powder after plastic working, processing distortion exists around the precipitated intermetallic compound. The maximum size of the magnesium alloy powder after plastic working is 10 mm or less, and the minimum size is 0.1 mm or more. The maximum grain size of the magnesium particles constituting the base of the magnesium alloy powder after plastic working is 20 m or less.

Preferably, the intermetallic compound is at least one selected from the group consisting of Mg ₁₇ Al ₁₂ , Al ₂ Ca, Mg ₂ Si, MgZn ₂ , Al ₃ Re (Re: Rare Earth Element), Al ₁₁ Re ₃ and Al ₆ Mn Compound. Moreover, Preferably, the largest particle diameter of an intermetallic compound is 5 micrometers or less, More preferably, it is 2 micrometers or less.

Preferably, the maximum grain size of the magnesium particles constituting the base of the magnesium alloy powder is 10 µm or less.

The high strength magnesium alloy according to the present invention is obtained by extrusion molding a magnesium alloy powder raw material having the above-mentioned characteristics, and is characterized by the following. That is, the maximum grain size of the magnesium particles constituting the base of the alloy is 10 µm or less, and the tensile strength at room temperature is 250 MPa or more.

Preferably, the maximum grain size of the magnesium particles constituting the base of the magnesium alloy is 5 µm or less, and the tensile strength at room temperature is 350 MPa or more.

Preferably, at least one selected from the group consisting of Mg ₁₇ Al ₁₂ , Al ₂ Ca, Mg ₂ Si, MgZn ₂ , Al ₃ Re (Re: Rare Earth Element), Al ₁₁ Re ₃ and Al ₆ Mn in the possession of a magnesium alloy One intermetallic compound is precipitated and dispersed.

Preferably, the magnesium alloy contains 0.5% or more and 4% or less of an active metal element selected from the group consisting of strontium (Sr), zirconium (Zr), scandium (Sc) and titanium (Ti).

The manufacturing method of the magnesium alloy powder raw material which concerns on this invention is a method of refine | finishing the crystal grain size of the magnesium particle which comprises the base material powder by carrying out plastic processing of starting material powder, and has the following characteristics. do. That is, as a starting raw material powder, magnesium alloy powder which precipitates and disperse | distributes a fine intermetallic compound by the heat processing is prepared. Plastic working is a plastic working in which the starting material powder is subjected to compression deformation or shear deformation through a pair of rolls to impart processing distortion around the intermetallic compound. The plastic working is repeated until the maximum size of the powder is 10 mm or less, the minimum size is 0.1 mm or more, and the maximum grain size of the magnesium particles constituting the base of the powder is 20 m or less.

In one embodiment, the step of preparing the magnesium alloy powder as starting material powder includes producing a magnesium alloy ingot by a casting method, solution treatment of the magnesium alloy ingot, followed by aging heat treatment, and the fineness of the ingot. Precipitating and dispersing an intermetallic compound, and taking out magnesium alloy powder by machining from an ingot. Preferably, when performing the above-mentioned plastic working, the temperature of the starting raw material powder to be added and the surface temperature of the roll in which the starting raw material powder is in contact with each other are set below the temperature of the aging heat treatment.

The method for producing a high strength magnesium alloy according to the present invention comprises the steps of obtaining a green compact by pressurizing the magnesium alloy powder raw material having the above-mentioned characteristics in a mold and a magnesium alloy green compact of 150 to 450 ° C. The process of heating to temperature, and the process of manufacturing a magnesium alloy by extruding a magnesium alloy compacted body immediately after completion | finish of heating are provided.

Preferably, the maximum grain size of the magnesium particles constituting the base of the magnesium alloy is 10 µm or less, and the tensile strength at room temperature is 250 MPa or more. More preferably, the magnesium alloy compact is heated at a temperature of 200 ° C or more and 350 ° C or less.

1 is a diagram showing a roller compactor device.

2 is a diagram showing a state in which processing distortion is present in the vicinity of an intermetallic compound.

Fig. 3 is a tissue photograph of AZ91D ingot, (a) is a tissue photograph after casting, (b) is a tissue photograph after solution heat treatment, and (c) is a tissue photograph after T6 heat treatment (solvation + aging heat treatment).

4 is an enlarged tissue photograph after the T6 heat treatment.

Fig. 5 is a tissue photograph of AZ91D powder subjected to plastic working with a roll, (a) a tissue photograph of T6 treatment, and (b) a tissue photograph of solution treatment.

The figure which shows the test result of the micro hardness (micro beaker hardness) of powder.

7 is a tissue photograph by an optical microscope of an extruded material, (a) is a tissue photograph when using a T6 heat-treated AZ91D powder, (b) is a tissue photograph when a solution-ized AZ91D powder is used.

8 is a structure photograph of the extrusion direction of the Mg alloy obtained by extruding and solidifying powder subjected to plastic processing by a roll 3, 10, 20, 30 times.

The pole figure of the result of having evaluated the orientation of the bottom face of magnesium.

EMBODIMENT OF THE INVENTION Below, embodiment and effect of this invention are demonstrated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. The magnesium alloy powder in which a fine intermetallic compound is deposited and dispersed by heat treatment is used as a starting material powder, which is passed through a pair of rolls. Mg alloy having a high tensile strength exceeding 250 to 350 MPa and a method for producing the coarse Mg alloy powder having a fine structure by compressive deformation and / or shear deformation are manufactured, and then pressed and extruded. It is to provide.

(1) Starting material powder and manufacturing method thereof

Mg is the main component, and other elements forming intermetallic compounds such as Al, Mn, Zn, Re (rare earth elements), Ca, and Si, strontium (Sr), zirconium (Zr), scandium (Sc), and titanium An Mg alloy ingot to which an active metal element selected from the group consisting of (Ti) is added is produced by a casting method. The Mg alloy ingot is subjected to a well-known T6 heat treatment (solvation heat treatment + aging heat treatment) to deposit and disperse the fine intermetallic compounds produced by the respective additive elements during the holding. Precipitated and dispersed intermetallic compounds are, for example, Mg ₁₇ Al ₁₂ , Al ₂ Ca, Mg ₂ Si, MgZn ₂ , Al ₃ Re (Re: rare earth element), Al ₁₁ Re ₃ , Al ₆ Mn, and the like. Since these intermetallic compounds are uniformly dispersed even in the presence of the Mg alloy after extrusion processing, they also contribute to the improvement of the yield strength. In addition, the strength can be further increased by containing 0.5% or more and 4% or less of active metal elements such as strontium (Sr), zirconium (Zr), scandium (Sc), and titanium (Ti).

Since the heat treatment conditions differ depending on the kind of the element to be added and the amount of the added elements, it is necessary to set appropriate conditions by observation of the structure, measurement of hardness (aging curing curve) and the like. Next, powder of a size of about 0.1 to 10 mm is collected from the Mg alloy ingot by machine or cutting processing such as price, and this is used as the starting material powder of the present invention. Moreover, when the particle diameter of powder is less than 0.1 mm, it will become easy to ignite, Therefore, from the standpoint of safety, the cutting powder used as 0.1 mm or more, More preferably, 0.5 mm or more is used.

(2) Magnesium Alloy Powder Raw Material and Manufacturing Method Thereof

Mg alloy powder subjected to the above T6 heat treatment is used as a starting material powder, and this is put into a roller compactor device shown in FIG.

The roller compactor apparatus shown in FIG. 1 includes a case 11, a multi-stage roll rotating body 12 disposed in the case 11, a shredding device 13, and a powder temperature and supply amount control system 14. And the receiving stand 15 is provided. The multi-stage roll rotating body 12 constitutes a plastic working part which performs plastic working on the starting material powder, and has three pairs of roll pairs 12a, 12b, and 12c which perform rolling processing. The starting material powder undergoes compression deformation and / or shear deformation as it passes between the paired rolls.

The starting raw material powder is adjusted to a predetermined temperature and a predetermined amount by the powder temperature / supply amount control system 14 and is introduced into the case 11. Here, predetermined temperature is below the temperature of the aging heat process mentioned later. The inside of the case 11 is maintained in an inert gas atmosphere, a non-oxidizing gas atmosphere, or a vacuum atmosphere from the viewpoint of preventing oxidation of the powder surface. In addition, the surface temperature of the multistage roll rotating body 12 and the atmospheric temperature in the case 11 are below the temperature of the aging heat treatment mentioned later.

The powder sent out from the roll pair 12c is subsequently crushed by the crushing device 13 to form granular powder. This granular powder may be returned to the powder temperature and supply amount control system 14 again, and the plastic processing by the multistage roll rotating body 12 may be repeated. The granular powder after processing is accommodated in the receiving stand 15.

The following structure control is performed by carrying out plastic processing which passes through a pair of rolls by compression deformation and / or shear deformation.

(a) As shown in FIG. 2, more processing distortion 22 is given to the periphery of the intermetallic compound particle 21 which precipitated and disperse | distributed in the possession of the magnesium alloy powder 20. FIG. The processing distortion 22 is a twinning, dislocation or the like introduced and accumulated around the intermetallic compound particles 21 by plastic working, and is observed in a transmission electron microscope (TEM). Seems.

(b) The maximum size of the powder after plastic working is 10 mm or less and the minimum size of the powder is 0.1 mm or more.

(c) It is assumed that it is relatively smaller with respect to the grain size of magnesium of the starting material powder.

(d) The maximum grain size of the magnesium particles constituting the powder body is set to 20 nm or less.

If necessary, after crushing, pulverizing, and sizing the Mg alloy powder raw material subjected to the plastic working by the roll, the plastic working by the roll is repeatedly performed under the same conditions. A Mg alloy powder raw material having a microstructure defined by the present invention is created.

First, with regard to (a), when plastic working is carried out by passing the powder between rolls, processing distortion is given to the whole powder. Since the intermetallic compound particles are precipitated and dispersed during the holding, the intermetallic compound is compared with the base. In the vicinity of the particles, more processing distortion is imparted. Therefore, by repeating this plastic working, more processing distortion accumulates around the intermetallic compound particles. When the processing distortion increases, the inventors of the present application generate many nucleation sites of dynamic recrystallization that occur during extrusion processing, which is a later step, and finer grains that could not be realized by the conventional method for producing Mg alloy. It was found that it could form.

Regarding this new knowledge, a similar technique is described in Japanese Patent Laid-Open No. 5-306404. In other words, a method of producing an Mg alloy member by press-molding an Mg alloy powder obtained by cutting from an Al-containing Mg alloy member subjected to T6 treatment by hot pressing and then extruding the molded body has been proposed. . However, the manufacturing method disclosed herein does not forcibly give rigid plastic working as proposed by the present invention to the T6-treated cutting Mg alloy powder, and as a result, the core of the dynamic recrystallization as described above. No formation site is formed, and fine grains are not obtained. For example, the tensile strength of Mg alloy in the case of using AZ80 alloy cutting powder subjected to T6 heat treatment is as low as about 200 MPa. In addition, as described above, the tensile strength of the extruded material in the case of using AZ80 powder not subjected to the T6 heat treatment is also 200 MPa, and there is no significant difference from that of the T6 heat treatment, and therefore, preferentially around the precipitated and dispersed particles, which is a feature of the present invention. It is fundamentally different from the manufacturing method that accumulates processing distortion and makes it a nucleation site for dynamic recrystallization.

In the present invention, the processing distortion is imparted in a random (disordered) direction by repeatedly performing plastic working with a pair of rolls on the powder. As a result, crystal orientation also becomes disordered in the Mg alloy after extrusion processing, and elongation improves. That is, in a normal extrusion material, although elongation falls by arrange | positioning the (0001) bottom surface which is a slip surface of Mg according to an extrusion direction, the kMg alloy powder which plastic-processed by a pair of rolls of this invention was extruded. In the case of processing, in addition to the (0001) bottom surface, non-bottom surfaces such as (10-10) main surface and (10-11) weight surface are also arranged along the extrusion direction. As a result, an Mg alloy having a high elongation in addition to high strength can be created.

Conversely, when the same plastic working was performed with a roller compactor on Mg alloy powder not subjected to T6 heat treatment, the fine grains of magnesium grains were confirmed, but the same fine crystals as in the case of T6 heat treatment were obtained. I didn't lose. Therefore, in order to refine the crystal grains by plastic working using a pair of rolls used in the present invention, it is necessary to precipitate and disperse the intermetallic compound particles in the possession of the Mg alloy powder raw material.

In addition, the size of the intermetallic compound particles has a strong correlation with the amount of processing distortion accumulated around the particles. The smaller the particle diameter of the intermetallic compound is, the more processing distortion can be accumulated, and as a result, an Mg alloy having a high yield strength can be obtained. Specifically, an Mg alloy having a high yield strength exceeding 250 MPa can be obtained by setting the maximum particle size of the intermetallic compound deposited and dispersed in the base material to 5 µm or less. In addition, when the maximum particle size of the intermetallic compound is 2 µm or less, more processing distortion can be accumulated with less plastic working. As a result, a high yield strength can be obtained, and an economic effect of producing an Mg alloy having fine grains and a high yield strength can be obtained under a condition that the number of times of plastic processing with a pair of rolls is reduced.

Therefore, the manufacturing method which plastic-processes the Mg alloy powder which precipitated and disperse | distributed the fine intermetallic compound particle by T6 heat processing beforehand through a pair of rolls, has a high yield strength which has the fine crystal grain in this invention. It is a characteristic for realizing Mg alloy which is compatible with high toughness.

Next, regarding (b), the maximum size of Mg alloy powder after plastic working by a pair of rolls is 10 mm or less, and the minimum size of powder is 0.1 mm or more. When the maximum size of the powder exceeds 10 mm, the bonding between the powders decreases during the compaction of the powder, which is the next step, or is not filled in the corners of the mold when the powder is injected into the mold. The problem arises that a defect occurs in (端 部). On the other hand, when the minimum size of Mg alloy powder is less than 0.1 mm, it will become easy to ignite, and the problem of handling safety arises.

In (c) and (d), by performing the plastic working with a pair of rolls, Mg alloy powder having a relatively smaller grain size with respect to the grain size of magnesium of the starting material powder is produced. Specifically, in the Mg alloy powder after plastic working by a pair of rolls, the maximum grain size of the magnesium particles constituting the base is 20 µm or less. By compression molding and extrusion processing such Mg alloy powder, an Mg alloy having a yield strength exceeding 250 MPa can be obtained. On the contrary, when the grain size of the magnesium particle of the powder after plastic working by a roll exceeds 20ULm, it is difficult to obtain a high yield strength exceeding 250 MPa in the Mg alloy produced using such Mg alloy powder. Further, in Mg alloys, in order to obtain a higher yield strength, for example, exceeding 350 MPa, it is necessary to make the crystal grain size of the Mg alloy powder after plastic working by a pair of rolls to be 10 Atm or less.

In the plastic working by roll, it is necessary to make the temperature of the starting raw material powder to put and the surface temperature of the roll which powder contacts contact below the aging heat treatment temperature in a post-processing process. When the plastic working is performed at a temperature higher than the aging heat treatment temperature, the amount of processing distortion accumulated in the periphery of the intermetallic compound particles due to the overaging phenomenon decreases, and the dynamic recrystallization during the extrusion processing does not proceed effectively. It becomes difficult to obtain a high strength Mg alloy having fine grains.

(3) Magnesium Alloy and its Manufacturing Method

The high strength Mg alloy having the following characteristics can be obtained by the compaction molding and the hot extrusion processing on the magnesium alloy powder raw material subjected to the plastic working by the above-mentioned rolls.

(a) The maximum crystal grain size of the magnesium particle which comprises the base material of the obtained Mg alloy is 10 micrometers or less.

(b) The tensile strength at room temperature of the alloy is 250 MPa or more.

The inventors of the present application, in particular, when using a raw material having a grain size of 10 μm or less of magnesium particles of Mg alloy powder, the maximum grain size constituting the base of the Mg alloy after extrusion processing is 5 μm or less, It was found that the tensile strength at room temperature became 350 MPa or more. In addition, Mg ₁₇ Al ₁₂ , Al ₂ Ca, Mg ₂ Si, MgZn ₂ , Al ₃ Re (Re: Rare Earth Element), Al ₁₁ Re ₃ and Al ₆ Mn, which are dispersed in the possession of the feedstock subjected to T6 treatment. Also with an intermetallic compound, the yield strength of the Mg alloy after extrusion processing improves.

The magnesium alloy powder raw material subjected to the plastic working by the above-mentioned roll is pressurized in the state filled with the metal mold | die, and a green compact is produced. After heating the molded object in the temperature range of 150 degreeC or more and 450 degrees C or less, it immediately solidifies by extrusion processing and manufactures a magnesium alloy material. If the heating temperature is lower than 150 ° C, fine magnesium crystal grains are not obtained because dynamic recrystallization does not proceed. On the other hand, when heating temperature exceeds 450 degreeC, the problem that a fine recrystallization structure grows and coarsens arises. In addition, in consideration of the influence of the processing calorific value at the time of extrusion processing, it is preferable to make the molded body temperature 200 degreeC or more and 350 degrees C or less. From the standpoint of densification, the extrusion ratio is 10 or more, more preferably 30 or more.

(Example 1)

After AZ91D ingots (composition-Al: 9.1, Zn: 0.85, Mn: 0.23% by weight, Mg: remainder) produced by the casting method were subjected to solution heat treatment (air-cooling after maintaining the heating at 413 DEG C for 16 hours), the aging was continued. Heat treatment (cooling in a furnace in a nitrogen gas atmosphere after heating and holding at 251 占 폚 for 4 hours) was performed. Powder was produced from this ingot by pulverizing (T6 heat-treated AZ91D powder).

On the other hand, as a comparison, in the state where only the solution heat treatment was performed for the cast ingot, powder was produced by pulverization under the same conditions (solution treatment AZ91D powder). The particle size of any powder was in the range of 0.5 to 4 mm.

Using each AZ91D powder as a starting material, plastic working was performed by a roller compactor apparatus. Here, the roll diameter was 100 mm, the circumferential speed of the roll was 100 mm / sec, the clearance between the rolls was 0.1 mm, the surface temperature of the rolls and the raw material powder temperature were all room temperature. A predetermined magnesium alloy powder (one pass product) was produced by pulverizing the plate-shaped connected powder subjected to plastic working by a roll to a length of 1 to 5 mm with a cutter mill device. By repeating this treatment, crystal grains were refined. Here, the powder in the case of repeating 20 times and 40 times is set to N = 20 and 40, respectively, and the case where plastic processing with a roll is not performed is set to N = 0.

Fig. 3 is a tissue photograph of the AZ91D ingot, (a) shows a tissue photograph after casting, (b) shows a tissue photograph after solution treatment, and (c) shows a tissue photograph after T6 treatment (solvation + aging heat treatment). As is apparent from the structure photograph of Fig. 3, by the solution treatment, the coarse Mg ₁₇ Al ₁₂ compound precipitated after casting is dissolved in magnesium holding, and aged by heat treatment, so that the fine intermetallic compound is uniformly held in the holding. It can be recognized that it is dispersed.

The tissue photograph which expanded the structure of AZ91D after T6 heat processing of FIG. 3 (c) is shown in FIG. The fine granular compound of 500-800 nanometers (nm) is disperse | distributed uniformly, and the predetermined structure structure aimed at by this invention in the starting raw material is formed by performing T6 heat processing.

5, the structure | tissue photograph of the AZ91D powder which plastic-processed by the roll is shown. (a) shows the structure after T6 treatment by this invention, and (b) has shown the structure in the case of only the solution treatment of a comparative example. In the case of using the AZ91D powder subjected to T6 treatment, it is recognized that by performing the plastic processing by the rolls 20 and 40 times, the magnesium base exhibits a homogeneous structure and the grain size is reduced to about 2 to 5 microns. . On the other hand, in the case of using the AZ91D powder subjected to the solution treatment of (b), even after 40 plastic workings, the substrate exhibits a heterogeneous mixed structure (the state where white and black areas are mixed in the photograph). Magnesium is composed of coarse grains exceeding 20 microns.

The microhardness (micro beaker hardness) test result of each powder is shown in FIG. In any starting material powder, the hardness increased with the increase in the number of times of plastic processing by the rolls, but the hardness of the AZ91D powder subjected to the T6 heat treatment showed a higher value. In addition, the difference in hardness between them increases with the increase in the number of times of processing. That is, it is recognized that the AZ91D powder subjected to the T6 heat treatment accumulates the processing deformation by plastic working using a roll more effectively.

(Example 2)

Each AZ91D powder produced in Example 1 was mold-molded at normal temperature using a hydraulic press, and the columnar extrusion billet was produced. After heating this billet for 400 degreeC * 5 minute (s) in nitrogen gas atmosphere, the dense bar was produced by immediately performing a warm extrusion process (extrusion ratio (r) = 37). Tensile test pieces (parallel portions 20 mm) were taken from each magnesium alloy extruded material, and a tensile test was performed at a strain rate of 10 ⁻⁴ per second at normal temperature. Table 1 shows the tensile strength (0.2% distortion), tensile strength, and elongation at break.

TABLE 1

By using the AZ91D powder subjected to the T6 treatment of the present invention, both the tensile strength and the 0.2% yield strength of the extruded material via the plastic working by the rolls were remarkably increased, and in particular, the tensile strength was 250 to 300 MPa. High values exceeded. In addition, the fracture elongation is maintained at a high value of about 18%. Thus, by using the manufacturing method of this invention, it is possible to manufacture the magnesium alloy which has high tensile strength and high toughness.

On the other hand, in the case of using the AZ91D powder, which was subjected only to the solution heat treatment, as a comparative example, the tensile strength and tensile strength increased as the number of plastic processing by the roll increased, but compared with the results of the T6 treated powder of the present invention, It can be seen that the value is low, in particular, the tensile strength does not reach 250 MPa.

The structure observation result by an optical microscope is shown in FIG. 7 about the extruded material at the time of performing the plastic processing by a roll 40 times. As shown in (a), when the T6 heat-treated AZ91D powder of the present invention was used, the crystal grain size distribution of magnesium base was measured by image analysis. As a result, the maximum grain size was 4.2 µm and the average grain size was 1.5 µm. During processing, microstructures were formed by dynamic recrystallization. On the other hand, in the case of using the solution-treated AZ91D powder as a comparative example of (b), the maximum grain size of the extruded material was 21 µm and the average grain size was 9.6 µm, which was remarkably higher than that of the T6 heat-treated AZ91D powder shown in (a). It is a huge organization. That is, by performing the plastic working process by the roll on the T6 heat-treated Mg alloy powder of the example of the present invention, more processing strain is accumulated around the fine intermetallic compound precipitates deposited and dispersed on the substrate, and as a result, dynamic recrystallization This was more effectively promoted to form fine grains.

(Example 3)

After the ZAXE1713 ingots (composition-Al: 7.1, ZNo.95, Ca: 0.93, La: 2.87 wt%, Mg: remainder) produced by the casting method, solution heat treatment (air cooling after heating and holding at 420 ° C for 16 hours) Then, aging heat treatment (cooling in a furnace in a nitrogen gas atmosphere after heating and holding at 180 ° C. for 36 hours) was performed. Powder was produced from this ingot by pulverizing (T6 heat treatment ZAXE1713 powder). On the other hand, as a comparison, powder was produced by grinding processing under the same conditions without heat-treating the cast ingot (ZAXE1713 powder without heat treatment). The particle size of any powder was in the range of 0.6 to 4 mm. Each ZAXE1713 powder was used as a starting material, and plastic working was performed by a roller compactor apparatus.

Here, as in Example 1, the roll diameter was 100 mm, the circumferential speed of the roll was 100 mm / sec, the clearance between the rolls was 0.1 mm, the surface temperature of the roll and the raw material powder temperature were all room temperature. Predetermined magnesium alloy powder (one pass product) was produced by pulverizing the plate-shaped connected powder subjected to plastic working by a roll to a length of 1 to 5 mm by a cutter mill apparatus. This was repeated to refine the crystal grains. Here, the maximum number of times of repetitive plastic processing by a roll is 30 times, and the case where plastic processing by a roll is not performed is set to N = 0.

Each ZAXE1713 powder was mold-molded at normal temperature using the hydraulic press, and the columnar extrusion billet was produced. After heating this billet for 400 degreeC * 5 minute (s) in nitrogen gas atmosphere, the dense bar was produced by immediately performing a warm extrusion process (extrusion ratio (r) = 37). Tensile test pieces (parallel portions 20 mm) were taken from each magnesium alloy extruded material, and a tensile test was performed at a deformation rate of 5 × 10 ⁻⁴ per second at normal temperature. Table 2 shows the results of measurement of tensile strength (0.2% distortion), tensile strength, and elongation at break.

TABLE 2

By using the ZAXE1713 powder subjected to the T6 treatment of the present invention, both the tensile strength and the 0.2% yield strength of the extruded material via the plastic working by the rolls were significantly increased, and in particular, the tensile strength exceeded 250 to 300 MPa. High values. The breaking elongation is also maintained at a high value of 16% or more. Thus, by using the manufacturing method of this invention, it is possible to manufacture the magnesium alloy which has high tensile strength and high toughness.

On the other hand, in the case of using the ZAXE1713 powder which was not subjected to the heat treatment as a comparative example, the tensile strength and the tensile strength increased with the increase in the number of plastic processing by the rolls, but compared with the results of the T6 heat-treated powder of the present invention, their values Is low, and in particular, the tensile strength does not reach 250 MPa.

About the ZAXE1713 powder which performed T6 heat processing, the structure observation result of the extrusion direction of the Mg alloy obtained by extruding and solidifying the powder which performed the plastic processing by roll 3, 10, 20, 30 times is shown in FIG. As the number of times of processing increases, the grain size of magnesium constituting the substrate becomes smaller. In particular, the maximum grain size is 9.2 µm and the average grain size is 4.8 µm at 20 times, and the maximum grain size is 4.4 µm at 30 times. , The average grain size was 1.2 μm.

(Example 4)

After AZ80A ingots (composition-Al: 8.2, Zn: 0.51, Mn: 0.18% by weight, Mg: remainder) produced by the casting method were subjected to solution heat treatment (air-cooling after heating and holding at 410 ° C. for 6 hours), aging was continued Heat treatment (cooling in a furnace in a nitrogen gas atmosphere after heating and holding at 175 占 폚 for 26 hours) was performed. Powder was produced from this ingot by pulverizing (T6 heat-treated AZ80A powder). On the other hand, as a comparison, powder was produced by grinding | pulverization processing under the same conditions, without heat-processing the cast ingot (heat processing AZ80A powder). The particle size of any powder was in the range of 0.6 to 4 mm.

Each AZ80A powder was used as a starting material, and plastic working was performed by a roller compactor apparatus. Here, as in Example 1, the roll diameter was 100 mm, the circumferential speed of the roll was 100 mm / sec, the clearance between the rolls was 0.1 mm, the surface temperature of the roll and the raw material powder temperature were all room temperature. A predetermined magnesium alloy powder (one pass product) was produced by pulverizing the plate-shaped connected powder subjected to plastic working by a roll to a length of 1 to 5 mm with a cutter mill device. This was repeated to refine the crystal grains. Here, the case where the plastic processing by a roll is not performed by making the repetition number of times of plastic processing with a roll into 50 at maximum is set to N = 0.

Each AZ80A powder was mold-molded at normal temperature using the hydraulic press, and the columnar extrusion billet was produced. After heating this billet for 400 degreeC * 5 minute (s) in nitrogen gas atmosphere, the dense bar was produced by immediately performing a warm extrusion process (extrusion ratio (r) = 37). Tensile test pieces (parallel portions 20 mm) were taken from each magnesium alloy extruded material, and a tensile test was performed at a deformation rate of 5 × 10 ⁻⁴ per second at normal temperature. Table 3 shows the results of measurements of tensile strength (0.2% distortion), tensile strength, and elongation at break.

TABLE 3

When AZ80A powder subjected to the T6 treatment of the present invention was subjected to plastic working with a roll, the tensile strength was high at 262 to 317 MPa, and also had a high elongation at break of 17.9 to 18.9%.

On the other hand, in the comparative example, even when T6 heat-treated AZ80A powder was used, the tensile strength was low as 208 MPa, unless plastic processing was performed by the roll. In the AZ80A powder not subjected to the heat treatment, the tensile strength is 218 MPa even when the plastic working with the roll is performed 20 times, which is remarkably lower than the example of the present invention.

(Example 5)

The extrusion billet was produced by metal mold | die using the kT6 heat processing ZAXE1713 powder produced by Example 3 (the number of times of plastic processing by a roll; 30 times). The magnesium alloy extrusion material was produced on the conditions shown in Table 4 when the billet heating temperature at the time of densely solidifying this by warm extrusion (extrusion ratio (r) = 37). Tensile test pieces (parallel portions 20 mm) were taken from each magnesium alloy extruded material, and a tensile test was performed at a deformation rate of 5 x 10 < ^-4 > Table 4 shows the results of measurements of tensile strength (0.2% distortion), tensile strength, and elongation at break.

TABLE 4

When the appropriate billet temperature defined by the present invention is satisfied, the tensile strength shows a high value exceeding 300 MPa. On the other hand, in the case where the billet temperature of the comparative example is 130 ° C, high tensile strength cannot be obtained because recrystallization in the extrusion process does not sufficiently proceed. In the case where the billet temperature of the comparative example is 480 ° C, high tensile strength cannot be obtained because fine recrystallized structures grow and coarsen in the extrusion process.

(Example 6)

Using the T6 heat-treated ZAXE1713 powder produced in Example 3, plastic working with a roll was performed up to 30 times under the same conditions as in Example 1, and the powder structure was refined. In that case, the temperature of the roll surface and powder was made into normal temperature or 200 degreeC together. The obtained Mg alloy powder was mold-molded at normal temperature by the hydraulic press, and the columnar extrusion billet was produced. After heating this billet for 400 degreeC * 5 minute (s) in nitrogen gas atmosphere, the compact bar material was produced by immediately performing a warm extrusion process (extrusion ratio (r) = 37). Tensile test pieces (parallel portions 20 mm) were taken from each magnesium alloy extruded material, and a tensile test was performed at a deformation rate of 5 × 10 ⁻⁴ per second at normal temperature. Table 5 shows the results of measurement of tensile strength (0.2% distortion), tensile strength, and elongation at break.

TABLE 5

When the temperature of the roll surface and powder which are the examples of this invention were made into normal temperature, the tensile strength, tensile strength, and elongation at break of the obtained Mg alloy extruded material showed the high value all.

On the other hand, when the temperature of the roll surface and powder which are comparative examples were set to 200 degreeC higher than the aging treatment temperature (175 degreeC), all the tensile strength and tensile strength fell significantly compared with the example of this invention. In particular, regarding the yield strength, a constant value was exhibited regardless of the increase in the number of times of processing. This is because when the plastic working with a roll is performed while the Mg alloy powder is heated above the aging treatment temperature, the processing distortion does not sufficiently accumulate around the precipitate due to overaging, and as a result, the dynamic during extrusion processing It is because the microstructure by recrystallization becomes difficult to be formed and the fall of the proof strength has arisen.

(Example 7)

The result of having evaluated the orientation of the bottom face 0001 of magnesium about the cross section of the AZ80A extrusion raw material produced in Example 4 is shown in the pole figure of FIG. Here, the number of times of plastic processing by a roll was made into 5, 10, 30, 50 times. Up to 10 times of processing, the (0001) plane forms an aggregate structure represented by a typical extruded material along the extrusion direction. However, at 30 times and 50 times, the bottom orientation is weakened, in other words, the non-bottom surfaces such as the (10-10) main surface and the (10-11) weight surface other than the (0001) bottom surface are also arranged along the extrusion direction.

On the other hand, in the Mg alloy powder which was not heat-treated, even after 50 times of plastic working, the remarkable fall of bottom orientation was not seen.

From the above results, after the plastic working using the roll specified in the present invention is applied to the T6 heat-treated Mg alloy powder, the Mg alloy material obtained by extrusion processing increases the tensile strength due to the refinement of crystal grains by dynamic recrystallization. In addition, an improvement in fracture elongation (toughness) occurs due to disorder of the aggregate tissue.

(Example 8)

The cast magnesium ingot having the composition shown in Table 6 was subjected to solution heat treatment (air cooling after heating and holding at 420 ° C. × 16 hours), and then aged in heat treatment (after cooling holding at 180 ° C. for 36 hours, in a nitrogen gas atmosphere). ).

TABLE 6

Magnesium alloy powder was produced from each ingot by grinding. The particle size of any powder was in the range of 0.6 to 4 mm. Using each powder as a starting material, plastic working was performed by a roller compactor apparatus. Here, as in Example 1, the roll diameter was 100 mm, the circumferential speed of the roll was 100 mm / sec, the clearance between the rolls was 0.1 mm, the surface temperature of the roll and the raw material powder temperature were all room temperature.

A predetermined magnesium alloy powder (one pass product) was produced by pulverizing the plate-shaped connected powder subjected to plastic working by a roll to a length of 1 to 5 mm with a cutter mill device. This was repeated to refine the crystal grains. Here, the number of repetitions of plastic working by a roll was 30 times. In addition, the case where plastic processing with a roll is not performed as a comparison is made into N = 0.

Subsequently, each process powder was metal-molded at normal temperature using the hydraulic press, and the columnar extrusion billet was produced. After heating this billet for 400 degreeC * 5 minute (s) in nitrogen gas atmosphere, the compact bar material was produced by immediately performing a warm extrusion process (extrusion ratio (r) = 37). Tensile test pieces (parallel portions 20 mm) were taken from each magnesium alloy extruded material, and a tensile test was performed at a deformation rate of 5 × 10 ⁻⁴ per second at normal temperature. Table 7 shows the results of measurements of tensile strength (0.2% distortion), tensile strength, and elongation at break.

TABLE 7

Samples Nos. 1 to 9 are examples of the present invention, and Samples Nos. 2 to 9 were powders obtained from a cast magnesium alloy ingot in which an active metal element such as Zr, Sr, Sc, and Ti was added to the sample No. 1 in an appropriate range. It is an extruded material obtained by using. Compared with the characteristic of sample No. 1, by adding active metal elements, such as Zr, Sr, Sc, and Ti, tensile strength and tensile strength can be improved, without accompanying significant fall of elongation (toughness).

On the other hand, in the samples Nos. 10 to 12 which are comparative examples, when plastic working by a roll was not performed, even if an active metal element was added, the increase of tensile strength and tensile strength was not recognized, but rather the fall of elongation occurred.

As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to what was shown embodiment. In the illustrated embodiment, various modifications and variations can be made within the same range as the present invention or within an equivalent range.

The present invention can be advantageously used to obtain a magnesium alloy that is compatible with high yield strength and elongation.

Claims (16)

In a magnesium alloy powder raw material having a relatively small grain size by performing a plastic working process in which the starting material powder having a relatively large grain size passes through a pair of rolls to be subjected to compression or shear deformation, The starting raw material powder is a magnesium alloy powder which precipitates and disperses the fine intermetallic compound in the substrate by heat treatment, In the magnesium alloy powder after the plastic working, processing distortion exists around the precipitated intermetallic compound, The maximum size of the magnesium alloy powder after the plastic working is 10 mm or less, the minimum size is 0.1 mm or more, Magnesium alloy powder raw material characterized in that the maximum grain size of the magnesium particles constituting the base of the magnesium alloy powder after the plastic working is 20㎛ or less. The method of claim 1, The intermetallic compound is at least one intermetallic selected from the group consisting of Mg ₁₇ Al ₁₂ , Al ₂ Ca, Mg ₂ Si, MgZn ₂ , Al ₃ Re (Re: rare earth element), Al ₁₁ Re ₃ and Al ₆ Mn Magnesium alloy powder raw material characterized by the above-mentioned. The method of claim 1, Magnesium alloy powder raw material characterized in that the maximum particle diameter of the said intermetallic compound is 5 micrometers or less. The method of claim 1, Magnesium alloy powder raw material characterized in that the maximum particle diameter of the said intermetallic compound is 2 micrometers or less. The method of claim 1, Magnesium alloy powder raw material, characterized in that the maximum grain size of the magnesium particles constituting the base of the magnesium alloy powder is 10㎛ or less. In the manufacturing method of the magnesium alloy powder raw material according to claim 1, A metal element selected from the group consisting of strontium (Sr), zirconium (Zr), scandium (Sc) and titanium (Ti) contains 0.5% or more and 4% or less by weight, and the balance is substantially magnesium (Mg). The manufacturing method of the magnesium alloy powder raw material made into. In the magnesium alloy obtained by extrusion-molding the magnesium alloy powder raw material according to claim 1, The maximum grain size of the magnesium particles constituting the base of the alloy is 10 μm or less, High tensile strength magnesium alloy, characterized in that the tensile strength of 250MPa or more at room temperature. The method of claim 7, wherein The maximum grain size of the magnesium particles constituting the base of the magnesium alloy is 5㎛ or less, High tensile strength magnesium alloy, characterized in that the tensile strength of 350MPa or more at room temperature. The method of claim 7, wherein At least one metal selected from the group consisting of Mg ₁₇ Al ₁₂ , Al ₂ Ca, Mg ₂ Si, MgZn ₂ , Al ₃ Re (Re: Rare Earth Element), Al ₁₁ Re ₃ and Al ₆ Mn in the possession of the magnesium alloy A high strength magnesium alloy, wherein the liver compound is precipitated and dispersed. In the method for miniaturizing the crystal grain size of the magnesium particles constituting the base material of the starting material powder by performing plastic working on the starting material powder, As the starting material powder, a magnesium alloy powder is prepared in which a fine intermetallic compound is deposited and dispersed in a substrate by heat treatment, The plastic working is plastic working which imparts processing distortion to the periphery of the intermetallic compound by compressing or shearing the starting material powder between a pair of rolls. The plastic working is repeatedly performed until the maximum size of the powder is 10 mm or less, the minimum size is 0.1 mm or more, and the maximum grain size of the magnesium particles constituting the powder is 20 m or less. Method for producing alloy powder raw material. The method of claim 10, The step of preparing a magnesium alloy powder as the starting material powder, Manufacturing a magnesium alloy ingot by a casting method, Solution treatment of the magnesium alloy ingot and subsequent aging heat treatment to deposit and disperse the fine intermetallic compound in the possession of the ingot; Method of producing a magnesium alloy powder raw material comprising the step of taking out the magnesium alloy powder by machining from the ingot. The method of claim 11, A method of producing a magnesium alloy powder raw material, wherein the temperature of the starting raw material powder to be introduced and the surface temperature of the roll in which the starting raw material powder is in contact with the firing processing are set to be equal to or less than the temperature of the aging heat treatment. The method of claim 11, The magnesium alloy ingot contains 0.5% or more and 4% or less by weight of a metal element selected from the group consisting of strontium (Sr), zirconium (Zr), scandium (sc) and titanium (Ti), with the balance being substantially magnesium The manufacturing method of the magnesium alloy powder raw material characterized by the above-mentioned. Pressurizing the magnesium alloy powder raw material according to claim 1 in a state filled with a mold to obtain a green compact; Heating the magnesium alloy compacted body at a temperature of 150 ° C. or more and 450 ° C. or less, And a step of extruding the magnesium alloy compacted body immediately after completion of the heating to produce a magnesium alloy. The method of claim 14, The method for producing a high strength magnesium alloy, characterized in that the maximum grain size of the magnesium particles constituting the base of the magnesium alloy is 10 µm or less, and the tensile strength at room temperature is 250 MPa or more. The method of claim 14, The magnesium alloy green compact is heated at a temperature of 200 ° C to 350 ° C.

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