【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
関するもので特に形状記憶特性を損なうことなく
冷間加工性と強度を向上せしめたものである。一
般に形状記憶合金は、マルテンサイト変態温度以
上の領域で所定形状に成形し、これをマルテンサ
イト変態温度以下の領域で変形した後、マルテン
サイト変態温度以上に加熱すると所定形状に回復
する性質を有し、またマルテンサイト変態温度近
傍において超弾性を示す性質を有するもので、
種々の合金が開発され、形状記憶効果や超弾性を
利用して種々の用途に用いられている。このよう
な形状記憶合金中Cu−Zn−Al系形状記憶合金は
価格的に有利なため各種用途への適用が検討され
用途によつては実用化されている。
従来Cu−Zn−Al系形状記憶合金は熱間加工
後、高温域（β相）で加熱処理してから冷間加工
を行つているが、加熱処理中に結晶粒が粗大化し
易く、場合によつては結晶粒が１〜３mmにも粗大
化し、冷間加工性を著しく損なう欠点があつた。
また結晶粒の粗大化は二方向性形状記憶効果の利
用において、繰返し使用回数（寿命）を短縮し、
超弾性の利用においてももともと弾性異方性が大
きいことから負荷応力方向の非選択性につながる
欠点があつた。
本発明はこれに鑑み種々研究の結果、従来粗大
結晶粒のため冷間加工が困難とされていたCu−
Zn−Al系形状記憶合金の組成にNiを添加し、さ
らにSi、Ｐのうち少なくとも１種を所定量添加す
ることによつてNiSi系、NiP系の金属間化合物
の析出により、結晶粒微細化を計り、冷間加工の
良好な合金を開発したものである。すなわち本発
明形状記憶合金はAl0.05〜10.0wt％（以下wt％
を単に％と略記する）とZn9.0〜40.0％、Ni0.30
〜2.0％を含み、Si、Ｐのうち少なくとも１種0.01
〜0.50％を含み残部がCuよりなることを特徴とす
るものである。
しかし本発明合金においてAl0.05〜10.0％、
Zn9.0〜40.0％、Ni0.30〜2.0％を含み、Si、Ｐの
うち少なくとも１種0.01〜0.50％と限定した理由
はAl0.05％、Zn9.0％未満では必要とする変態温
度が低過ぎるばかりか形状記憶効果が得られない
こともあり、また添加元素のNiが0.30％未満、
Si、Ｐのうち少なくとも１種類0.01％未満では必
要とする微細な組織が得られず、さらにAlが10.0
％、Znが40.0％を超えると、γ相の析出により冷
間加工を悪化させるばかりか、形状記憶効果が得
られないこともあり現実的でない。またNiが2.0
％を超え、さらにSi、Ｐのうち少なくとも１種類
が0.50％を超えると微細な組織は得られるが、形
状記憶効果を損なわせるという欠点があるからで
ある。
以下本発明合金を実施例について説明する。黒
鉛るつぼを使用してCuを溶解し、その湯面を木
炭粉末で覆い十分溶解した後Si、Ｐのうち少なく
とも１種類とZn、Al、Niを添加し、これを鋳造
し第１表に示す組成の長さ180mmのインチバーと
幅150mm、長さ200mm、厚さ25mmの鋳塊を得た。
次にこれらの鋳塊の表面をそれぞれ一面あたり
2.5mm面削した後、熱間圧延を行い直径８mmの棒、
幅150mm、厚さ８mmの板とした。これらの棒、板
について冷間加工性、引張り強さ、形状記
憶性を調査した結果を第１表に示す。なお比較の
ため第１表に結晶粒微細化させるための添加元素
Ni、Si、Ｐを全く添加していないCu−Zn−Al系
形状記憶合金についても併記した。
冷間加工法は上記棒および板を600〜700℃の温
度に加熱焼鈍した後、冷間加工しその加工率が80
％可能で表面にササクレ、割れの見られないもの
を○印、加工率が70％では表面にササクレ、割れ
が見られないが加工率が80％で表面にササクレ、
割れが発生しているものを△印、加工率が80％で
断線あるいは割れ破壊が発生したものを×印で表
わした。
引張り強さの測定は全試料の加工率を60％と一
律にし、JIS−Z2241により行つた。
形状記憶効果の測定はコイル径10mm、コイル長
50mm、線径１mmのコイルをMf点（マイテンサイ
ト変態終了温度）より30℃低い温度でコイル長さ
を100mmまで伸ばし、これをAf点（マルテンサイ
ト逆変態終了温度）より30℃高い温度で加熱した
とき完全にもとのコイル長50mmに縮むものを○
印、完全にもとのコイル長50mmまで縮まないもの
を×印とした。
The present invention relates to the improvement of Cu-Zn-Al type shape memory alloys, and in particular improves cold workability and strength without impairing shape memory properties. In general, shape memory alloys have the property of being formed into a predetermined shape in a region above the martensitic transformation temperature, deformed in a region below the martensitic transformation temperature, and then recovering to the predetermined shape when heated above the martensitic transformation temperature. It also has the property of exhibiting superelasticity near the martensitic transformation temperature,
Various alloys have been developed and used for various purposes by taking advantage of shape memory effects and superelasticity. Among these shape memory alloys, Cu--Zn--Al type shape memory alloys are advantageous in terms of price, so their application to various applications has been studied and, depending on the application, they have been put into practical use. Conventionally, after hot working, Cu-Zn-Al shape memory alloys are heat-treated in a high temperature range (β phase) and then cold-worked, but the crystal grains tend to coarsen during the heat treatment, and in some cases Eventually, the crystal grains became coarse to 1 to 3 mm, resulting in a drawback that the cold workability was significantly impaired.
In addition, the coarsening of crystal grains shortens the number of repeated uses (life) when utilizing the bidirectional shape memory effect.
Even in the use of superelasticity, there is a drawback that the elastic anisotropy is originally large, leading to non-selectivity in the direction of applied stress. In view of this, the present invention was developed as a result of various researches.
By adding Ni to the composition of the Zn-Al type shape memory alloy and further adding a predetermined amount of at least one of Si and P, crystal grains are refined by precipitation of NiSi type and NiP type intermetallic compounds. We have developed an alloy that can be easily cold-worked. In other words, the shape memory alloy of the present invention has an Al content of 0.05 to 10.0wt% (hereinafter wt%
is simply abbreviated as %), Zn9.0~40.0%, Ni0.30
Contains ~2.0% and at least one of Si and P 0.01
It is characterized by containing ~0.50% Cu, with the remainder being Cu. However, in the alloy of the present invention, Al0.05-10.0%,
The reason why it is limited to 0.01 to 0.50% of at least one of Si and P, including 9.0 to 40.0% of Zn and 0.30 to 2.0% of Ni is that the required transformation temperature is lower than 0.05% of Al and 9.0% of Zn. Not only is it too low, but the shape memory effect may not be obtained, and the added element Ni is less than 0.30%.
If at least one of Si and P is less than 0.01%, the required fine structure cannot be obtained, and if Al is less than 0.01%,
%, Zn exceeding 40.0% not only deteriorates cold working due to the precipitation of γ phase but also makes it impossible to obtain the shape memory effect, which is not realistic. Also, Ni is 2.0
%, and furthermore, if at least one of Si and P exceeds 0.50%, a fine structure can be obtained, but there is a drawback that the shape memory effect is impaired. Examples of the alloy of the present invention will be described below. Melt Cu using a graphite crucible, cover the hot water surface with charcoal powder, and after sufficiently melting, add at least one of Si and P, Zn, Al, and Ni, and cast it as shown in Table 1. An inch bar with a composition length of 180 mm and an ingot with a width of 150 mm, a length of 200 mm, and a thickness of 25 mm were obtained. Next, the surface of each of these ingots is
After face cutting 2.5mm, hot rolling is performed to create a bar with a diameter of 8mm.
The plate was 150 mm wide and 8 mm thick. Table 1 shows the results of investigating the cold workability, tensile strength, and shape memory properties of these bars and plates. For comparison, Table 1 shows additive elements for grain refinement.
A Cu-Zn-Al type shape memory alloy to which no Ni, Si, or P is added is also described. In the cold working method, the above bars and plates are heated and annealed to a temperature of 600 to 700°C, and then cold worked to a processing rate of 80%.
If the processing rate is 70%, the surface is cracked, and if the processing rate is 80%, there are no cracks, but the surface is cracked.
Those in which cracks have occurred are indicated by a △ mark, and those in which disconnection or cracking has occurred at a processing rate of 80% are indicated by an × mark. The tensile strength was measured in accordance with JIS-Z2241, with a uniform processing rate of 60% for all samples. The shape memory effect was measured using a coil diameter of 10 mm and coil length.
Stretch a coil of 50 mm and wire diameter 1 mm to 100 mm at a temperature 30°C lower than the Mf point (martensite transformation end temperature), and then heat it at a temperature 30°C higher than the Af point (martensite reverse transformation end temperature). ○ If the coil length completely shrinks to the original 50 mm when
A coil that did not completely shrink to its original length of 50 mm was marked with an x.
【表】
第１表から明らかなように本発明合金は引張り
強さが96〜112Kg／mm2の特性を示し良好な冷間加
工性と良好な形状記憶性とを有していることがわ
かる。
これに対しNi、Si、Ｐ含有量が本発明合金の
組成範囲より少ない比較合金No.891011では形状記
憶性は良好であるが、いずれも冷間加工性は改善
されず、引張り強さも本発明合金の同様なAl量
の合金と比較しても劣ることがわかる。またNi、
Si、Ｐ含有量が本発明合金の組成範囲より多い比
較合金No.121314では冷間加工性は十分であるが、
いずれも形状記憶性が劣つていることがわかる。
以上詳述したように本発明合金はすぐれた冷間
加工性、引張り強さと十分な形状記憶性を併せ持
ちCu−Zn−Al系形状記憶合金として顕著な効果
を奏するものである。[Table] As is clear from Table 1, the alloy of the present invention exhibits a tensile strength of 96 to 112 Kg/mm 2 and has good cold workability and good shape memory. . On the other hand, comparative alloy No. 891011, which has a lower Ni, Si, and P content than the composition range of the present alloy, has good shape memory, but cold workability is not improved in any of them, and the tensile strength is also lower than that of the present invention alloy. It can be seen that the alloy is inferior when compared with alloys with similar Al content. Also Ni,
Comparative alloy No. 121314, which has Si and P contents higher than the composition range of the present alloy, has sufficient cold workability, but
It can be seen that both have poor shape memory properties. As detailed above, the alloy of the present invention has excellent cold workability, tensile strength, and sufficient shape memory, and exhibits remarkable effects as a Cu-Zn-Al shape memory alloy.