CN104046868A - Rare-earth-free low-cost high-strength heat-conducting magnesium alloy and preparation method thereof - Google Patents

Abstract

A rare-earth-free, low-cost, high-strength, heat-conducting magnesium alloy and its preparation method, its chemical composition weight percent is: Mn0.5-2.0wt%, Ca0.3-1.5wt%, Al0.3-1.0wt%, and the rest is Mg and unavoidable impurities. The invention solves the problems existing in the existing heat-conducting magnesium alloys, such as using a variety of rare earth elements or high-priced alloying elements that lead to high cost, or increasing the content of alloying elements in order to increase the strength, resulting in a sharp drop in thermal conductivity and high alloy density. Alloys have relatively high thermal conductivity, strength and flame resistance, and are relatively low in cost and relatively low in density.

Description

A rare earth-free low-cost high-strength heat-conducting magnesium alloy and its preparation method

technical field

The invention relates to the field of metal materials and metal material processing, in particular to a rare-earth-free, low-cost, high-strength, heat-conducting magnesium alloy and a preparation method thereof.

Background technique

Magnesium is the lightest of commonly used metal structural materials, with a specific gravity of about 1.74g/cm ³ , which is 1/4 of steel and 2/3 of aluminum. Magnesium and magnesium alloys have the three advantages of rich resources, energy saving, and environmental friendliness, and are lightweight structural materials and functional materials with high specific strength. They are recognized by the world as "the most promising new materials in the 21st century"".

The thermal conductivity of pure magnesium at room temperature is high, about 157W/m*K, but the strength is too low, and the tensile yield strength in the as-cast state is about 21MPa. After magnesium is alloyed, its strength is significantly improved, but the thermal conductivity is usually significantly reduced. For example, the thermal conductivity of the existing commercial alloy Mg-3Al-1Zn (AZ31) alloy is 78W/m*K, Mg-9Al-1Zn (AZ91 ) alloy thermal conductivity is 55W/m*K, Mg-6Al-0.5Mn (AM60) alloy thermal conductivity is 61W/m*K (Magnesium, MagnesiumAlloys, and Magnesium Composites, by Manoj Gupta and Nai Mui Ling, Sharon), they The thermal conductivity is much lower than that of pure magnesium. At present, magnesium alloy radiators basically use the above-mentioned commercial magnesium alloys with low thermal conductivity, and the heat dissipation effect of magnesium alloys is far from fully exerted.

In recent years, my country's electronic technology has developed rapidly, and the development trend of high performance, miniaturization and integration of the electronic industry has greatly increased the total power density and calorific value of electronic devices, and the problem of heat dissipation has become more and more prominent, especially sensitive to weight reduction requirements. The complex structural parts of the heat dissipation system of aerospace devices, portable electrical appliances, communication equipment, vehicles and other products require not only excellent thermal conductivity, but also the characteristics of low density, excellent mechanical properties and low production cost. Therefore, taking into account thermal conductivity Lightweight thermally conductive magnesium alloy materials with high mechanical properties and production and processing properties have an irreplaceable role and an important application background. However, there are few domestic and foreign reports on the influence of alloy elements on the thermal conductivity of magnesium alloys and their mechanisms. It is urgent to carry out composition design of thermally conductive magnesium alloys, and develop new high thermal conductive magnesium alloys and related preparation technologies.

Some alloys with relatively high thermal conductivity have been publicly reported abroad, such as EZ33 (100W/m*K, Mg-RE-Zn), QE22 (113W/m*K, Mg-Ag-RE), ZE41 (123W/m*K K, Mg-Zn-RE), etc., but their strengths are all low.

In recent years, some higher-strength thermally conductive magnesium alloys have been gradually developed in China. For example, the alloy composition disclosed in Chinese Patent Publication No. CN100513606C contains 2.5-11% Zn, 0.15-1.5% Zr, 0.1-2.5% Ag, 0.3- 3.5% Ce, 0-1.5% Nd, 0-2.5% La, Pr0-0.5%; 20°C thermal conductivity greater than 120W/m*K, tensile strength greater than 340MPa, yield strength greater than 310MPa. However, these heat-conducting magnesium alloys all contain a large amount of rare earth elements such as Nd, La, Pr, Ce, etc., or alloy elements such as Ag, Zr, etc., the cost of the alloy is high, and the material density is relatively high.

Chinese Patent Publication No. CN101709418 proposes another heat-conducting alloy whose chemical composition is 1-6.5% Zn, 0.2-2.5% Si; thermal conductivity at 20°C is greater than 120W/m*K, tensile strength is 265-380MPa, yield The strength is 210~355MPa. When the content of main alloying element Zn is low, the mechanical properties are low (tensile strength<340MPa, yield strength<310MPa); while when the content of heavy alloying element Zn (~6.5%) is high, the material density is high (>1.8g/ cm ³ ). And according to reports, due to the existence of low melting point Mg-Zn phase, the hot workability is average; the ignition point of the alloy is low (about 600 ° C), and the flame resistance is poor. Therefore, in order to better meet the low-cost, low-density, and high-performance requirements of consumer electronics, automotive and other industries for thermally conductive magnesium alloys, there is an urgent need to develop magnesium alloys with lower cost, lower density, higher strength, and better thermal conductivity. , Flame-resistant new magnesium alloy heat dissipation structural material.

Contents of the invention

In view of the problems existing in the existing heat-conducting magnesium alloys, such as using a variety of rare earth elements or high-priced alloying elements that lead to high cost, or increasing the content of alloying elements in order to increase the strength, resulting in a sharp drop in thermal conductivity and high alloy density, the purpose of the present invention is to The invention aims to provide a rare earth-free, low-cost, high-strength, heat-conducting magnesium alloy and a preparation method thereof. The magnesium alloy has relatively high thermal conductivity, strength and flame resistance, relatively low cost, and relatively low density.

For achieving the above object, technical scheme of the present invention is:

A rare-earth-free, low-cost, high-strength, heat-conducting magnesium alloy, the chemical composition of which is: Mn0.5-2.0wt%, Ca0.3-1.5wt%, Al0.3-1.0wt%, the rest is Mg and unavoidable Impurities.

At present, the metal materials used for radiators are mostly aluminum alloys or copper alloys. The study found that the thermal conductivity of the alloy is closely related to the amount and type of solid solution atoms and second phases in the alloy. The thermal conductivity of magnesium alloys also follows a similar principle. To design a new type of heat-conducting alloy and improve the thermal conductivity of magnesium alloy, the number of solid-solution atoms in magnesium alloy should be properly controlled, and at the same time, the size and number of precipitated phases should not be too large.

Alloying elements commonly used in magnesium alloys include Al, Zn, Mn, Ca, RE, etc. The research concluded that the design principle of high-strength magnesium alloys is: the atomic radius of the main alloying elements is larger than that of magnesium atoms, and the other is smaller than that of magnesium atoms. , which is conducive to the formation of regular G.P regions of monoatomic or polyatomic layers, nanoscale precipitates, and stable high-melting point precipitates like aluminum alloys during deformation, so that the alloy has higher strength and high temperature resistance. According to the above theory, the present invention finds that magnesium, aluminum, calcium, and manganese elements have a good matching relationship by calculating alloying elements commonly used in magnesium. In the Mg-Al-Ca-Mn quaternary alloy, the atomic radius of Ca atoms is larger than that of Mg atoms, and the atomic radii of Al and Mn atoms are smaller than that of Mg atoms. At the same time, the negative value of the mixing enthalpy between Ca-Al and Al-Mn atoms is relatively large. .

According to the respective characteristics of each element in magnesium, the type and amount of alloying elements in this scheme can be optimally designed from the perspective of alloy strengthening mechanism in materials science, and then the phase diagram of magnesium alloy and the performance characteristics of the actual cast alloy can be used to design verify.

Al is the most commonly used alloying element in magnesium alloys, and its density is small. Aluminum can form a limited solid solution with magnesium, which can improve the casting performance while increasing the strength and hardness of the alloy, and can also produce aging strengthening through heat treatment. According to the literature, the thermal conductivity of magnesium-aluminum alloy decreases with the increase of the number of solid-solution atoms, so the content of aluminum element needs to be controlled to maintain good thermal conductivity. Ca is a metal element with a small specific gravity. The element can effectively refine the grains in magnesium, inhibit the oxidation of molten magnesium, increase the ignition temperature and flame resistance of the alloy melt, and improve the creep properties of the alloy. According to literature reports, the Mg-Al-Ca ternary phase diagram is calculated by thermodynamic software: when the ratio of Al/Ca is changed, three different second phases may appear in the alloy, and the number of the second phases increases with the addition of elements. increase gradually. In particular, ordered single-layer GP regions can be obtained in this alloy, and the strengthening effect of this nanostructure on the alloy is very obvious. Therefore, in order to control the amount and type of the second phase present in the alloy and maintain the low density of the alloy, low alloying should be used; but in order to ensure the strengthening effect to obtain higher alloy strength, there must be a sufficient amount of second phase particles Therefore, the content of Al and Ca in the design alloy is greater than 0.3%, but not more than 1.5%. The design ranges of Al and Ca content in the present invention are respectively: Al=0.3～1.0wt%, Ca=0.3～1.5wt%.

Mn controls the iron content by precipitating Fe-Mn compounds, and improves the corrosion behavior by controlling the iron content; at the same time, the Mn manganese element in magnesium can increase heat resistance, refine grains, and strengthen alloys. As shown in the figure below, after adding 0.1-0.5% Mn element to Mg-6Al-3Ca alloy, its creep resistance increases significantly and heat resistance improves. However, the solid solubility of manganese in magnesium is small, and the content generally does not exceed 1.0wt%. In the environment where the second phase can be formed, if there is Al element, increasing the content of manganese in an appropriate amount may form a certain amount of AlMn strengthening phase while solid-solving part of the manganese element in the matrix, which is conducive to further improving the mechanical properties of the alloy. The present invention designs the content of Mn to be 0.5-2wt%.

The second phase of the Mg-Al-Ca-Mn alloy designed by the present invention is mainly Mg ₂ Ca, Al ₂ Ca, Al ₈ Mn ₅ precipitates, and its melting point is relatively high (Mg ₂ Ca, Al ₂ Ca, Al ₈ Mn ₅ 714°C, 1079°C, and 1160°C respectively), which have good thermal stability and strengthening effect, which is conducive to ensuring the heat resistance and high mechanical properties of the alloy.

The preparation method of rare earth-free low-cost high-strength heat-conducting magnesium alloy of the present invention is characterized in that it comprises the following steps:

1) Use pure metal or intermediate alloy as raw material, and carry out batching according to the above-mentioned magnesium alloy composition;

2) Put the pure metal and the intermediate alloy into the crucible of the smelting furnace and melt them to prepare alloy ingots;

3) cutting the rare earth-free heat-conducting magnesium alloy ingot into corresponding billets;

4) Heating the billet to the predetermined deformation temperature for deformation treatment, the deformation temperature range is 300-500°C, and the deformed billet should be heated to the required deformation temperature within 10 minutes; the deformation treatment adopts rolling, extrusion or forging process One or more of them can obtain the required rare-earth-free, low-cost, high-strength, heat-conducting magnesium alloy material.

Further, the complete melting of pure magnesium and Mg-Mn master alloy in step 2) is carried out under the protection of CO ₂ and SF ₆ mixed protective gas, the flow ratio of CO ₂ and SF ₆ is 40-100, and the temperature of the solution after melting is controlled At 710-760°C; Al ingots are heated to 250-310°C in the preheating furnace, and the preheated Al ingots, Ca particles or Mg-Ca master alloys are successively added to the magnesium melt, and argon gas is required when adding Ca Stir, then keep warm for 5-10 minutes; use metal mold casting or semi-continuous casting.

Furthermore, in step 3), before cutting the non-rare earth thermally conductive magnesium alloy ingot into corresponding blanks, the alloy ingot is heated to 490-515° C. under the protection of an argon atmosphere for 0.1-48 hours of homogenization treatment.

In addition, the deformation treatment in step 4) adopts the rolling process to deform the blank into a plate, adopts the extrusion process to deform the blank into a pipe, bar or profile, and adopts the forging process to deform the blank to process various forgings; the above-mentioned A variety of processes for composite deformation.

Preferably, the deformation treatment in step 4) adopts a rolling process, the rolling deformation speed is 10-40m/min, the single-pass reduction is 30%-50%, and the cumulative deformation of the plate is ≥ 90%;

Preferably, the preparation method of rare earth-free low-cost high-strength heat-conducting magnesium alloy according to claim 2 is characterized in that the deformation treatment in step 4) adopts an extrusion process, and the extrusion deformation speed is 0.2-30m/min. The pressure ratio is 10-50.

Preferably, the deformation treatment in step 4) adopts a forging process, the forging deformation speed is 0.1-30m/min, the reduction in a single pass is 30%-50%, and the cumulative deformation is ≥ 60%.

Alloy materials can obtain better mechanical properties through grain refinement, which can not only improve their processing plasticity, but also improve their strength. Compared with other alloys such as iron and aluminum, magnesium alloy has a larger K coefficient of the Hall-Petch relationship, and the contribution of its grain refinement to the strength of the alloy is more obvious. In order to obtain finer grains and further improve the strength, toughness and other excellent properties of magnesium alloys, hot deformation processing is generally used to refine grains. During deformation processes such as extrusion, rolling, forging, etc., the coarse second phase formed by casting is gradually broken and refined, and dispersed in the magnesium matrix, which further improves the mechanical properties of the alloy. Plastic deformation such as rolling, extrusion or forging can significantly improve the strength and ductility of magnesium and magnesium alloys. Comprehensive mechanical properties. The mechanical properties of the high thermal conductivity magnesium alloys of Chinese patents CN100513606C and CN101709418 have been significantly improved after deformation such as extrusion.

During the smelting process, the alloy of the invention has a stable melt temperature and still has good fire resistance when the melt temperature reaches 650°C. After the alloy is deformed, the tensile strength at room temperature (25°C) is greater than 340MPa, and the tensile yield strength is greater than 330MPa.

The magnesium alloy does not contain any rare earth elements and high-valent alloy elements, the thermal conductivity at 20°C is greater than 125W/(m*K), and the density is less than 1.8g/cm ³ . It can be used as structural material for heat dissipation system of aerospace, computer, communication and consumer electronics products as well as LED lighting products.

Compared with the existing heat-conducting magnesium alloy, the heat-conducting magnesium alloy product of the present invention has the following significant advantages:

1. Low alloy cost: The rare earth-free, low-cost, high-strength, thermally conductive magnesium alloy prepared by the present invention is composed of conventional alloying elements Al, Ca, and Mn, without adding expensive rare earth elements and other high-priced elements.

2. The alloy melt is stable, and the ignition point is obviously increased (higher than 650°C).

3. Low alloy density: within the range of composition design, the density of all designed alloys is less than 1.80g/cm ³ .

4. High thermal conductivity: the rare earth-free low-cost high-strength thermal conductivity magnesium alloy prepared by the present invention has a thermal conductivity greater than 125W/(m*K) at 20°C, and the thermal conductivity of the alloy is still good when the temperature rises.

5. High mechanical properties: the tensile strength at room temperature (25°C) is greater than 340MPa, and the tensile yield strength is greater than 330MPa.

6. Excellent comprehensive performance: Compared with the existing magnesium alloy, its thermal conductivity and strength are relatively high, but the cost is relatively low, and the alloy density is relatively small. It is widely used in aerospace, computer, communication and consumer electronics products and LED lighting products. It has broad application prospects in the structural materials of the heat dissipation system.

Description of drawings

Fig. 1 is the variation curve of material thermal conductivity with temperature after hot extrusion of Mg-Mn-Ca-Al alloys with different element ratios in the embodiment of the present invention;

Fig. 2 is the room temperature tensile mechanical curve of the Mg-Mn-Ca-Al alloy with different element ratios in the embodiment after hot extrusion.

Detailed ways

The technical solution of the present invention will be described in detail below through the examples and accompanying drawings. The present embodiment is implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operating procedures are provided, but the protection scope of the present invention does not Limited to the following examples.

Select three alloy components Mg-1.5Mn-1.0Al-1.0Ca (wt%) (alloy 1), Mg-1.5Mn-1.0Al-0.5Ca (wt%) (alloy 2), Mg-1.5Mn-0.5Al -1.0Ca (wt%) (alloy 3) as a typical example.

According to the technical scheme of the present invention, pure metals or intermediate alloys are used as alloying raw materials to produce low-cost magnesium alloy ingots through smelting; the addition of Ca element inhibits the oxidation of molten magnesium and increases the ignition temperature of the alloy melt (higher than 650 ° C), The degree of oxidation of the alloy is significantly reduced during the smelting process. Put the extruded billet into the induction heating furnace and heat it rapidly to the extrusion temperature of 350°C, and then directly deform the billet into a bar by extrusion process, the extrusion speed is 5m/min, the extrusion ratio is 25, after extrusion Bars are air-cooled. And the extruded rods were tested, the results showed that:

After hot extrusion of Alloy 1, the thermal conductivity coefficients in the range of 20, 100, 200 and 270°C were 129.4, 131.3, 133.5 and 135.1W/(m*K) respectively (as shown in Figure 1); at room temperature (25 ℃) The tensile strength is 371MPa, the tensile yield strength is 356MPa, the elongation is about 6% (as shown in Figure 2); the density is about 1.78g/cm ³ .

After hot extrusion of alloy 2, the thermal conductivity coefficients in the range of 20, 100, 200 and 270 °C are 137.2, 137.8, 138 and 138.2 W/(m*K) respectively (as shown in Figure 1); at room temperature (25 ℃) The tensile strength is 360MPa, the tensile yield strength is 350MPa, the elongation is about 6% (as shown in Figure 2); the density is about 1.78g/cm ³ .

After hot extrusion, the thermal conductivity of alloy 3 in the range of 20, 100, 200 and 270°C is 125.3, 126.1, 126.8 and 127.1W/(m*K) respectively (as shown in Figure 1); at room temperature (25 ℃) The tensile strength is 352MPa, the tensile yield strength is 346MPa, the elongation is about 6% (as shown in Figure 2); the density is about 1.78g/cm ³ .

See Table 1 for other embodiments of the present invention.

Example 1

The design selects the Mg-1.5Mn-0.5Al-1.0Ca (wt%) alloy composition ratio to form a magnesium alloy, and the preparation method of its rare earth-free low-cost high-strength heat-conducting magnesium alloy is as follows:

1) With pure Mg ingot, pure Al ingot, pure Ca particles and Mg-5Mn master alloy (that is, the composition content of the master alloy is: 5wt% Mn, the rest is Mg) raw materials, according to the weight percentage of the above-mentioned magnesium alloy composition Ingredients;

2) After cleaning and preheating the crucible, put all the pure magnesium ingots and Mg-5Mn master alloy into the crucible of the melting furnace, and heat up under the protection of the mixed protective gas of CO ₂ and SF ₆ at a heating rate of 20-40 °C/min, the flow ratio of CO ₂ and SF ₆ is 50, and the temperature of the melt after complete melting is controlled at 710-760 °C;

3) Heat the pure Al ingot in a preheating furnace to 250-310°C, add the preheated Al ingot and Ca particles into the magnesium melt one after another, blow argon to stir when adding Ca, and then stir with a machine for 3 minutes After holding the heat for 8 minutes, all the alloy elements are evenly distributed in the magnesium solution, and finally the metal mold casting is used to prepare a non-rare earth thermally conductive magnesium alloy ingot;

4) Cut the heat-conducting magnesium alloy ingots prepared above directly into corresponding extrusion billets, and then directly adopt the extrusion process to deform the billets into rods after preheating at 350°C. The extrusion speed is 5m/min, and the extrusion The ratio is 25, and the bar is cooled by air cooling after extrusion, that is, rare earth-free, low-cost, high-strength, heat-conducting magnesium alloy can be obtained.

The heat conduction magnesium alloy material has a thermal conductivity of 125W/(m*K) at 20°C, a room temperature (25°C) tensile strength of 352MPa, a tensile yield strength of 346MPa, and an elongation of 6%.

Example 2

The design selects Mg-0.8Mn-0.5Al-0.5Ca (wt%) chemical composition ratio to form a magnesium alloy, and the preparation method of its rare earth-free low-cost high-strength heat-conducting magnesium alloy material is as follows:

1) With pure Mg ingot, pure Al ingot, Mg-30Ca and Mg-5Mn master alloy as raw material, carry out batching according to the weight percentage of above-mentioned magnesium alloy composition;

2) After cleaning and preheating the crucible, put all the pure magnesium ingots and Mg-5Mn master alloy into the crucible of the melting furnace, and heat up under the protection of the mixed protective gas of CO ₂ and SF ₆ at a heating rate of 20-40 °C/min, the flow ratio of CO ₂ and SF ₆ is 50, and the temperature of the melt after complete melting is controlled at 710-760 °C;

3) Put the pure Al ingot in the preheating furnace and heat it to 250-310°C, add the preheated Al ingot and the Mg-Ca master alloy into the magnesium melt successively, and blow argon to stir when adding Ca, and then the machine Stir for 3 minutes and keep warm for 10 minutes, so that all alloy elements are evenly distributed in the magnesium solution, and finally use metal mold casting to prepare a non-rare earth thermally conductive magnesium alloy ingot;

4) Directly cut the heat-conducting magnesium alloy ingot prepared above into corresponding rolling billets, and then preheat at 430°C, with the roll speed at 20m/min, the single-pass reduction at 30-50%, and the cumulative deformation 90%, rolled into plates, to obtain rare earth-free low-cost high-strength heat-conducting magnesium alloy.

The heat conduction magnesium alloy material has a thermal conductivity of 126W/(m*K) at 20°C, a room temperature (25°C) tensile strength of 360MPa, a tensile yield strength of 352MPa, and an elongation of 10%. (as attached)

Example 3

The design selects the Mg-1.5Mn-0.9Al-1.0Ca (wt%) alloy composition ratio to form a thermally conductive magnesium alloy, and the extrusion profile preparation method is as follows:

1) Proportioning alloy raw materials and smelting and pouring into ingot according to the method described in embodiment 1;

2) Cut the heat-conducting magnesium alloy ingot prepared above directly into corresponding extrusion billets, and then directly adopt the extrusion process to deform the billets into forming materials after preheating at 350°C. The extrusion speed is 3m/min, and the extrusion ratio 25, the extruded material is cooled by air cooling, that is, a rare earth-free, low-cost, high-strength, heat-conducting magnesium alloy can be obtained.

The prepared rare earth-free low-cost high-strength thermally conductive magnesium alloy has a thermal conductivity of 129W/(m*K) at 20°C, a room temperature (25°C) tensile strength of 370MPa, a tensile yield strength of 355MPa, and an elongation of 7%. .

Example 4

The design selects the Mg-1.0Mn-0.3Al-1.5Ca (wt%) alloy composition ratio to form a magnesium alloy, and the preparation method of its rare earth-free low-cost high-strength heat-conducting magnesium alloy is as follows:

1) Proportioning alloy raw materials and smelting and pouring into semi-continuous ingot according to the method described in embodiment 1;

2) Cut the heat-conducting magnesium alloy ingot prepared above directly into corresponding forging blanks, and then deform the blanks into forgings by forging after preheating at 420°C. The forging deformation speed is 0.5m/min, and the single-pass pressing The lower weight is 30% to 50%, and the cumulative deformation is 90%, so that rare earth-free, low-cost, high-strength and heat-conducting magnesium alloy forgings are obtained.

The thermal conductivity of the forged part material at 20°C is 130W/(m*K), the tensile strength at room temperature (25°C) is 359MPa, the tensile yield strength is 350MPa, and the elongation is 8%.

Example 5

The design selects Mg-2.0Mn-0.5Al-0.3Ca (wt%) chemical composition ratio to form a magnesium alloy, and the preparation method of its rare earth-free low-cost high-strength heat-conducting magnesium alloy material is as follows:

1) Proportioning alloy raw materials and smelting and pouring into ingot according to the method described in embodiment 2;

2) Directly cut the heat-conducting magnesium alloy ingot prepared above into corresponding rolling billets, and then preheat at 420°C, with the roll speed at 20m/min, the single-pass reduction at 30-50%, and the cumulative deformation 90%, rolled into plates, to obtain rare earth-free low-cost high-strength heat-conducting magnesium alloy.

Tested along the rolling direction, the thermal conductivity of the material at 20°C is 128W/(m*K), the tensile strength at room temperature (25°C) is 362MPa, the tensile yield strength is 347MPa, and the elongation is 5%.

Example 6

The design selects the Mg-2.0Mn-0.5Al-1.4Ca (wt%) alloy composition ratio to form a magnesium alloy, and the preparation method of its rare earth-free low-cost high-strength heat-conducting magnesium alloy is as follows:

1) Proportioning alloy raw materials and smelting and pouring into ingot according to the method described in embodiment 1;

2) Cut the heat-conducting magnesium alloy ingot prepared above directly into corresponding forging blanks, and then deform the blanks into forgings by forging after preheating at 440°C. The forging deformation speed is 0.5m/min, and the single pass pressing The lower weight is 30% to 50%, and the cumulative deformation is 80%, so that rare earth-free, low-cost, high-strength and heat-conducting magnesium alloy forgings are obtained.

The thermal conductivity of the forged part material at 20°C is 127W/(m*K), the tensile strength at room temperature (25°C) is 346MPa, the tensile yield strength is 338MPa, and the elongation is 6%. (as attached)

Example 7

The design selects the Mg-1.5Mn-1.0Al-0.5Ca (wt%) alloy composition ratio to form a magnesium alloy, and the preparation method of its rare earth-free low-cost high-strength heat-conducting magnesium alloy is as follows:

1) Proportioning alloy raw materials and smelting and pouring into ingot according to the method described in embodiment 1;

2) Cut the heat-conducting magnesium alloy ingot prepared above directly into corresponding extrusion billets, and then directly adopt the extrusion process to deform the billets into rods after preheating at 350°C. The extrusion speed is 5m/min, and the extrusion The ratio is 25, and the bar is cooled by air cooling after extrusion, that is, rare earth-free, low-cost, high-strength, heat-conducting magnesium alloy can be obtained.

The heat conduction magnesium alloy material has a thermal conductivity of 137W/(m*K) at 20°C, a room temperature (25°C) tensile strength of 360MPa, a tensile yield strength of 350MPa, and an elongation of 6%. (as attached)

Example 8

The design selects the Mg-1.5Mn-1.0Al-1.0Ca (wt%) alloy composition ratio to form a magnesium alloy, and the preparation method of its rare earth-free low-cost high-strength heat-conducting magnesium alloy is as follows:

1) Proportioning alloy raw materials and smelting and pouring into semi-continuous ingot according to the method described in embodiment 1;

2) Cut the heat-conducting magnesium alloy ingot prepared above directly into corresponding extrusion billets, and then deform the billets into rods by extrusion process after preheating at 350°C. The extrusion speed is 5m/min, and the extrusion ratio for 25. After extrusion, cut the bar and continue to process it by forging deformation at 350°C to obtain rare earth-free, low-cost, high-strength, heat-conducting magnesium alloy.

The heat conduction magnesium alloy material has a thermal conductivity of 129W/(m*K) at 20°C, a room temperature (25°C) tensile strength of 375MPa, a tensile yield strength of 358MPa, and an elongation of 7%.

Table 1

Claims (8)

1. A rare-earth-free, low-cost, high-strength, heat-conducting magnesium alloy, its chemical composition weight percentage is: Mn0.5～2.0wt%, Ca0.3～1.5wt%, Al0.3～1.0wt%, the rest is Mg and not Avoid impurities. the 2. the preparation method of rare earth-free low-cost high-strength heat-conducting magnesium alloy as claimed in claim 1, is characterized in that, comprises the following steps: 1) taking pure metal or intermediate alloy as raw material, carrying out batching according to the magnesium alloy composition described in claim 1; 2) Put the pure metal and the intermediate alloy into the crucible of the smelting furnace and melt them to prepare alloy ingots; 3) cutting the rare earth-free heat-conducting magnesium alloy ingot into corresponding billets; 4) Heating the billet to the predetermined deformation temperature for deformation treatment, the deformation temperature range is 300-500°C, and the deformed billet should be heated to the required deformation temperature within 10 minutes; the deformation treatment adopts rolling, extrusion or forging process One or more of the processes are used to obtain the required rare earth-free, low-cost, high-strength, heat-conducting magnesium alloy material. the 3. the preparation method of low-cost high-strength heat-conducting magnesium alloy without rare earth as claimed in claim 2 is characterized in that, in step 2) pure magnesium and Mg-Mn master alloy are completely melted in CO ₂ and SF ₆ mixed protection It is carried out under gas protection, the flow ratio of CO ₂ and SF ₆ is 40-100, and the temperature of the melt after melting is controlled at 710-760°C; the Al ingot is heated to 250-310°C in the preheating furnace, and the preheated Al ingots and Ca particles are successively added to the magnesium melt. When Ca is added, argon blowing is required to stir, and then the heat preservation is carried out for 5 to 10 minutes; metal mold casting or semi-continuous casting is adopted. 4. the preparation method of rare-earth-free low-cost high-strength heat-conducting magnesium alloy as claimed in claim 2, it is characterized in that, in step 3), before the non-rare-earth heat-conducting magnesium alloy ingot is cut into corresponding billet, the alloy ingot is placed in argon Under the protection of air atmosphere, heat to 490-515°C for 0.1-48 hours of homogenization treatment. the 5. The preparation method of rare earth-free low-cost high-strength heat-conducting magnesium alloy as claimed in claim 2, it is characterized in that, in step 4), deformation treatment adopts rolling process to process billet deformation into plate, and adopts extrusion process to deform the billet It is processed into pipe, bar or profile, and the blank is deformed by forging process to process various forgings; the above-mentioned multiple processes can also be used for compound deformation. the 6. The preparation method of rare earth-free low-cost high-strength heat-conducting magnesium alloy as claimed in claim 2, it is characterized in that, in step 4), deformation treatment adopts rolling process, rolling deformation speed is 10～40m/min, single pass The secondary reduction is 30% to 50%, and the cumulative deformation of the plate is ≥90%. the 7. The preparation method of rare earth-free, low-cost, high-strength, heat-conducting magnesium alloy as claimed in claim 2, characterized in that, the deformation treatment in step 4) adopts an extrusion process, and the extrusion deformation speed is 0.2～30m/min, and the extrusion process The ratio is 10-50. the 8. The preparation method of rare earth-free, low-cost, high-strength, heat-conducting magnesium alloy as claimed in claim 2, characterized in that the deformation treatment in step 4) adopts a forging process, the forging deformation speed is 0.1-30m/min, and the single-pass pressure The lower amount is 30% to 50%, and the cumulative deformation is ≥60%. the