【発明の詳細な説明】[Detailed description of the invention]
本発明は、Cu−Zn−Al系形状記憶合金の改良
に関するもので、形状記憶効果（Shape
Memory Effect：以下SMEと略す）に影響を及
ぼすことなく、冷間加工性や強度を向上させたも
のである。
一般に形状記憶合金は、母相領域で所定形状に
成形を施し、その後、マルテンサイト変態温度以
下のマルテンサイト相領域で変形を行つた後、母
相領域まで加熱される事により、所定形状に回復
する。又、マルテンサイト逆変態温度以上の温度
域では、負荷時に、見かけ上、塑性変形を起こし
ているように見えるが、除荷に際しては、逆変態
によつて、ひずみを回復する疑弾性
（Pseudoelasticity：以下PEと略す）を示すもの
で、SMEやPEを利用して種々の応用がなされて
いる。そして、このような形状記憶合金のうちで
も、Cu−Zn−Al系形状記憶合金は、コスト的に
安価である為、各種用途が検討されており、用途
によつては、実用化されている。しかしながら、
Cu−Zn−Al系形状記憶合金は温度域での熱処理
にともなう再結晶化過程において、結晶粒が容易
に粗大化し、粒径が１〜３mm程度に、なり、冷間
加工性を著しく悪化させる。結晶粒の粗大化は、
二方向性形状記憶効果（Two Way SME）やPE
の利用において繰り返し疲労特性（寿命）を短縮
する等の欠点を生じている。
本発明は、上記理由を種々検討の結果、Cu−
Zn−Al系形状記憶合金にCr，Ｐの複合添加する
ことにより、SMEに影響を及ぼすことなしに熱
処理における結晶粒の粗大化を抑制し、良好な微
細結晶粒が得られる合金で、Al0.05〜10.0wt％、
Zn9.0〜40.0wt％を含み、Cr及びＰを各々0.001〜
0.8wt％含み、残部Cuからなる事を特徴とするも
のである。
本発明において合金組成を上記の如く限定した
のはZn及びAlは形状記憶効果を得るためと、焼
入れ性向上のために含まれているものであるが、
Zn9.0wt％未満、Al0.05wt％未満ではSMEを示
さず、又Znが40.0wt％、Alが10.0wt％を超える
とSME、冷間加工性ともに悪いため、上記範囲
に決定した。
次にCr、Ｐを複合添加するのは、合金のSME
に影響を及ぼすことなく、熱処理での結晶粒の粗
大化を、防止し、又Cr3Ｐ、Cr2Ｐ、CrP、CrP2等
の金属間化合物及びCr単体の析出により微細結
晶粒を得るためであり、その結果、冷間加工性、
強度の向上をはかるものである。Cr及びＰの添
加量が0.001wt％未満では、微細化の効果は不十
分であり、Cr及びＰの添加量が0.8wt％を超える
と、SMEを損うためである。
以下、本発明合金の実施例について説明する。
黒鉛ルツボを用いて、電気銅を溶解し、湯面を
木炭粉末で覆い、Cr，Ｐ，Zn，Alを順次添加し
て第１表に示すような組成合金を溶製し、長さ
180mmのインチバーと、幅150mm厚さ25mm長さ200
mmの鋳塊に鋳造した。この鋳塊表面を一面当たり
2.5mm面削した後、熱間圧延により、直径８mmの
棒と幅150mm厚さ８mmの板を作製し、600〜700℃
の温度で焼鈍した後、棒については伸線加工を行
い、板については冷間圧延を行つて冷間加工性を
調査した。引張強さ、形状記憶特性・結晶粒径に
ついては前記試料を850℃の温度に10分間保持焼
鈍後、氷水中に焼入れた焼入れ材で測定を行つ
た。これらの結果を第１表に併記した。
The present invention relates to the improvement of Cu-Zn-Al based shape memory alloys, including the shape memory effect (shape memory effect).
It has improved cold workability and strength without affecting the memory effect (hereinafter abbreviated as SME). In general, shape memory alloys are formed into a predetermined shape in the matrix region, then deformed in the martensitic phase region below the martensitic transformation temperature, and then heated to the matrix region to recover the desired shape. do. In addition, in the temperature range above the martensite reverse transformation temperature, plastic deformation appears to occur during loading, but upon unloading, pseudoelasticity (pseudoelasticity) occurs in which the strain is recovered by reverse transformation. (hereinafter abbreviated as PE), and various applications have been made using SME and PE. Among these shape memory alloys, Cu-Zn-Al type shape memory alloys are inexpensive, so various uses are being considered, and some have even been put into practical use. . however,
The crystal grains of Cu-Zn-Al shape memory alloys easily become coarse during the recrystallization process associated with heat treatment in the temperature range, and the grain size becomes approximately 1 to 3 mm, which significantly deteriorates cold workability. . The coarsening of crystal grains is
Two-way shape memory effect (Two Way SME) and PE
However, when using this method, there are disadvantages such as shortening of cyclic fatigue characteristics (life). As a result of various studies on the above reasons, the present invention has developed Cu-
By adding Cr and P in combination to the Zn-Al shape memory alloy, coarsening of crystal grains during heat treatment can be suppressed without affecting SME, and good fine crystal grains can be obtained.Al0. 05~10.0wt%,
Contains Zn9.0~40.0wt%, Cr and P each 0.001~
It is characterized by containing 0.8wt% Cu, with the remainder being Cu. In the present invention, the alloy composition is limited as described above because Zn and Al are included to obtain a shape memory effect and to improve hardenability.
If Zn is less than 9.0 wt% and Al is less than 0.05 wt%, SME will not be exhibited, and if Zn exceeds 40.0 wt% and Al exceeds 10.0 wt%, both SME and cold workability will be poor, so the above range was determined. Next, Cr and P are added in combination to the alloy SME.
To prevent coarsening of crystal grains during heat treatment without affecting the process, and to obtain fine crystal grains by precipitation of intermetallic compounds such as Cr 3 P, Cr 2 P, CrP, CrP 2 and Cr alone. As a result, cold workability,
This is intended to improve strength. If the amount of Cr and P added is less than 0.001 wt%, the effect of refining is insufficient, and if the amount of Cr and P added exceeds 0.8 wt%, SME will be impaired. Examples of the alloy of the present invention will be described below. Using a graphite crucible, electrolytic copper is melted, the hot water surface is covered with charcoal powder, Cr, P, Zn, and Al are sequentially added to produce an alloy with the composition shown in Table 1.
180mm inch bar, width 150mm thickness 25mm length 200
It was cast into a mm ingot. One side of this ingot surface
After face milling 2.5 mm, a bar with a diameter of 8 mm and a plate with a width of 150 mm and a thickness of 8 mm were produced by hot rolling at 600 to 700℃.
After annealing at a temperature of , the bars were wire drawn and the plates were cold rolled to investigate cold workability. The tensile strength, shape memory properties, and crystal grain size were measured using the quenched material, which was annealed at a temperature of 850° C. for 10 minutes and then quenched in ice water. These results are also listed in Table 1.
【表】
第１表中、冷間加工性は加工率70％を境にして
表面にササクレや割れ、断線が発生しないものを
「○」、発生するものを「×」印で示した。
また、引張強さはJIS Ｚ 2241に基いて測定し
たものである。
形状記憶特性は、直径2.0mmの伸線加工材で、
直径10mm、全長50mmのコイルを作成し、所定の熱
処理を施した後、マルテンサイト変態温度以下の
温度域でコイルを長さ100mmまで伸ばし、次にマ
ルテンサイト逆変態温度以上の温度域に加熱した
時、コイルが元の形状に完全に戻るものを「○」、
完全に戻らないものを「×」印で示した。
次に結晶粒径についてはミクロ組織写真を光学
顕微鏡で撮影したものの、結晶粒を測定し、その
平均値が0.2mm以下のものを「小」、0.2〜1.0mmの
ものを「中」、1.0mm以上のものを「大」とした。
第１表からも明らかなようにCu−Zn−Al系形
状記憶合金にCr，Ｐを複合添加した本発明合金
は良好な冷間加工性と優れた形状記憶特性を示
し、引張強さは70〜90Kg／mm2の性能を有し、従来
合金No.18に比較して、冷間加工性・引張強さ・微
細結晶粒等の諸性質において、優れており、Al
又はZnの含有量の少ない比較合金No.11、No.12は
SMEを示さず、逆に含有量の多い比較合金No.13、
No.14はSME、冷間加工性ともに悪い。又、Cr，
Ｐの添加量の両方とも多いもの、片方だけ多いも
の、１種のみである比較合金No.15、No.16、No.17は
本発明合金よりも諸特性は大きく劣つている。
このように、本発明合金は、優れた冷間加工性
や引張強度、SME、微細結晶粒を有し、寿命や
超弾性等の諸性能に優れたもので工業的利用にお
いて顯著な効果を示すものである。[Table] In Table 1, cold workability is indicated by an "○" mark if no cracking, cracking, or wire breakage occurs on the surface at a working rate of 70%, and an "x" mark if such occurrences occur. Moreover, the tensile strength was measured based on JIS Z 2241. The shape memory property is a wire-drawn material with a diameter of 2.0 mm.
After creating a coil with a diameter of 10 mm and a total length of 50 mm and subjecting it to the specified heat treatment, the coil was stretched to a length of 100 mm at a temperature below the martensite transformation temperature, and then heated to a temperature above the martensite reverse transformation temperature. "○" means that the coil completely returns to its original shape when
Items that did not return completely were marked with an "x". Next, regarding the crystal grain size, microstructure photographs were taken with an optical microscope, and the crystal grains were measured. Those with an average value of 0.2 mm or less are considered "small," those with an average value of 0.2 to 1.0 mm are "medium," and 1.0 Those larger than mm were considered "large." As is clear from Table 1, the alloy of the present invention, which is a combination of Cu-Zn-Al shape memory alloy with Cr and P added, exhibits good cold workability and excellent shape memory properties, and has a tensile strength of 70. It has a performance of ~90Kg/ mm2 , and is superior to conventional alloy No. 18 in terms of properties such as cold workability, tensile strength, and fine grains.
Or comparative alloys No. 11 and No. 12 with low Zn content are
Comparative alloy No. 13, which does not show SME but has a high content,
No. 14 has poor SME and cold workability. Also, Cr,
Comparative alloys No. 15, No. 16, and No. 17, in which both amounts of P are added, those in which only one is large, and those in which only one type is added, have various properties that are significantly inferior to the alloys of the present invention. As described above, the alloy of the present invention has excellent cold workability, tensile strength, SME, fine crystal grains, and has excellent properties such as life and superelasticity, and exhibits remarkable effects in industrial applications. It is something.