JP2005281728A - SHAPE MEMORY ELEMENT MADE OF Ti-BASED ALLOY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape memory element made of a Ti-based alloy, which has superior biocompatibility and shows at least 2% recovery strain. <P>SOLUTION: The shape memory element is made of a Ti-based alloy which includes 4-10 atom% Mo, and 3-10 atom% Sn or 1-10 atom% Sc, and the balance Ti with unavoidable impurities. Then, the shape memory element shows at least 2% recovery strain. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、非Niバネ材に関し、特に、人体のあらゆる個所に一次的或いは永久に使用される生体材料として好適なTi基合金形状記憶素子に関するものである。   The present invention relates to a non-Ni spring material, and more particularly to a Ti-based alloy shape memory element suitable as a biomaterial used primarily or permanently in any part of the human body.

Ti-Ni系形状記憶合金がマルテンサイト変態の逆変態に付随して顕著な形状記憶効果および超弾性を示すことが良く知られている。これら合金から得られた形状記憶素子は、次に述べるような用途に使用されている。例えば、形状記憶効果用途として、形状記憶素子は、エアコン、電子レンジなどの感温アクチュエータに使われている。また超弾性用途として、形状記憶素子は、カテーテルガイドワイヤ、ステントなどの医療材料、メガネフレーム、ブレスレットなどの生活関連材料として広く使われている。しかしながら、生体との直接接触はNiによる金属アレルギーあるいは細胞毒性の問題発生の懸念から、その応用にはTi-Ni合金に樹脂などのコーティングがなされている。   It is well known that a Ti-Ni shape memory alloy exhibits a remarkable shape memory effect and superelasticity accompanying the reverse transformation of the martensitic transformation. Shape memory elements obtained from these alloys are used for the following applications. For example, as a shape memory effect application, a shape memory element is used for a temperature sensitive actuator such as an air conditioner or a microwave oven. As superelastic applications, shape memory elements are widely used as medical materials such as catheter guide wires and stents, and life-related materials such as eyeglass frames and bracelets. However, direct contact with a living body has concerns about the occurrence of metal allergy or cytotoxicity problems due to Ni, and Ti-Ni alloy is coated with resin or the like for its application.

近年、Niを含まず金属アレルギーを起こさない元素からなるTi基合金が検討されている。例えば、特許文献１には、β型Ti合金にAg(銀)が1〜 2wt%含む耐腐食性チタン合金が開示されている。また、特許文献２には、6wt%≦Mo(モリブデン)≦18wt％および0.5wt％≦Sn≦10wt％、残部がTiの冷間加工用低強度・高延性Ti合金が開示されている。さらに、特許文献３には、特許文献２と同様のTi合金が開示されている。一方、特許文献４においては、チタンに10〜15wt％のMoを含有させた形状記憶チタン合金が開示されている。   In recent years, Ti-based alloys composed of elements that do not contain Ni and do not cause metal allergy have been studied. For example, Patent Document 1 discloses a corrosion-resistant titanium alloy containing 1 to 2 wt% of Ag (silver) in a β-type Ti alloy. Patent Document 2 discloses a low-strength, high-ductility Ti alloy for cold working with 6 wt% ≦ Mo (molybdenum) ≦ 18 wt% and 0.5 wt% ≦ Sn ≦ 10 wt% with the balance being Ti. Further, Patent Document 3 discloses the same Ti alloy as Patent Document 2. On the other hand, Patent Document 4 discloses a shape memory titanium alloy in which 10 to 15 wt% of Mo is contained in titanium.

特開昭53-123323号公報JP-A-53-123323 特開平1-129941号公報Japanese Unexamined Patent Publication No. 1-129941 特開平4-214830号公報(特許第2936754号公報)Japanese Laid-Open Patent Publication No. 4-214830 (Patent No. 2936754) 特開昭59-56554号公報(特公昭59-35978号公報)JP 59-56554 (JP-B 59-35978)

しかしながら、前述した特許文献１には、実施例として数種のβ型Ti合金における耐腐食性向上が確認されているが、すべてのβ型Tiの耐腐食性が向上するとは限らず、ばね性についてはなんら記載されていない。特許文献２においては、高加工性、低強度の合金が紹介されているが、ばね性についての記載はない。特許文献３において、さらに加工性の向上した合金を取り上げ、その際、0.5〜6wt％のSnを有した合金が取り上げられているが、共に加工性の向上を図った低強度の合金に過ぎず、必ずしもばね性を有する物ではない。また、特許文献４においては、形状記憶特性を有する合金であり、Alの添加によりα安定化させ、応力誘起のマルテンサイトが形状記憶特性を示すが、ばね性についてはなんら記載されていない。特に、特許文献１〜４において、生体適合性を考慮したものは一つもない。   However, in Patent Document 1 described above, improvement in corrosion resistance in several types of β-type Ti alloys has been confirmed as an example. However, not all β-type Ti has improved corrosion resistance, and spring properties are improved. Is not described at all. In Patent Document 2, an alloy with high workability and low strength is introduced, but there is no description about spring property. In Patent Document 3, an alloy with further improved workability is taken up, and in that case, an alloy having 0.5 to 6 wt% of Sn is taken up, but both are only low-strength alloys with improved workability. It is not necessarily a thing with springiness. Further, in Patent Document 4, although it is an alloy having shape memory characteristics, α is stabilized by addition of Al, and stress-induced martensite exhibits shape memory characteristics, but there is no description about spring properties. In particular, none of Patent Documents 1 to 4 takes biocompatibility into consideration.

本発明者らは、加工性が良く、生体適合性に優れた生体用合金であり、毒性およびアレルギー性の指摘が少ない高強度なTi基合金ばね材を提供することを目的として、Ti-Mo基合金バネ（特願２００２−３４８６７４号）およびTi-Sc系形状記憶合金（特願２００２−３７０９９９号）を提案した。ここで本発明者らは、先願発明の中から、形状記憶効果導出可能な組成、製造条件および超弾性導出可能な組成、製造条件をそれぞれ抽出し、実用的な形状記憶素子を提供するものである。   In order to provide a high strength Ti-based alloy spring material, which is a bioalloy excellent in workability and excellent in biocompatibility and has little indication of toxicity and allergenicity, the present inventors have made Ti-Mo. A base alloy spring (Japanese Patent Application No. 2002-348874) and a Ti-Sc shape memory alloy (Japanese Patent Application No. 2002-370999) were proposed. Here, the present inventors extract a composition capable of deriving a shape memory effect, a manufacturing condition, a composition capable of deriving a superelasticity, and a manufacturing condition from the invention of the prior application, and provide a practical shape memory element. It is.

本発明によれば、以下の組成から成るTi基形状記憶素子が得られる。   According to the present invention, a Ti-based shape memory element having the following composition is obtained.

すなわち、本発明の第１の態様によれば、Moを４〜１０at％含み、およびSnを３〜１０at%若しくはScを１〜１０at%含み、残部がTi及び不可避不純物からなるTi合金であって、少なくとも２％の回復ひずみを示すTi基形状記憶素子が得られる。また、本発明によれば、前記Ti合金であって、β変態温度以上での熱処理後時効処理を行うことで、少なくとも３％以上の形状記憶効果或いは２％以上の超弾性を示すTi基形状記憶素子が得られる。   That is, according to the first aspect of the present invention, there is provided a Ti alloy containing 4 to 10 at% Mo and 3 to 10 at% Sn or 1 to 10 at% Sc, with the balance being Ti and inevitable impurities. A Ti-based shape memory element exhibiting a recovery strain of at least 2% is obtained. According to the present invention, the Ti alloy is a Ti-based shape that exhibits a shape memory effect of at least 3% or a superelasticity of 2% or more by performing an aging treatment after heat treatment at a β transformation temperature or higher. A memory element is obtained.

本発明の第２の態様によれば、Scを１at％以上およびNbを１５〜３０at%含み、残部がTi及び不可避不純物からなるTi合金であって、少なくとも２％の回復ひずみを示すTi基形状記憶素子が得られる。また、本発明によれば、前記Ti合金であって、β変態温度以上での熱処理後時効処理を行うことで、少なくとも３％ 以上の形状記憶効果或いは２％以上の超弾性を示すTi基形状記憶素子が得られる。   According to the second aspect of the present invention, the Ti-based shape is a Ti alloy containing 1 at% or more of Sc and 15 to 30 at% of Nb, with the balance being Ti and inevitable impurities, and exhibiting a recovery strain of at least 2%. A memory element is obtained. According to the present invention, the Ti alloy is a Ti-based shape that exhibits a shape memory effect of at least 3% or a superelasticity of 2% or more by performing an aging treatment after heat treatment at a β transformation temperature or higher. A memory element is obtained.

次に、組成および時効条件限定理由について説明する。   Next, the reasons for limiting the composition and aging conditions will be described.

・Ti-Mo-(Sn,Sc)系合金
Moを４〜10at％としたのは、４at％未満ではβ安定化が十分に図れず、加工性、特性劣化を招き、10at％を超えると十分な形状記憶特性が得難くなるためである。Sn、Scについてもその添加効果が顕著な範囲とし、特にScは極めて高価なためその効果が十分な範囲に限定した。また、時効条件限定は硬度の上昇影響を及ぼさない条件としたためである。 ・ Ti-Mo- (Sn, Sc) alloy
The reason why Mo is 4 to 10 at% is that β stabilization cannot be sufficiently achieved if it is less than 4 at%, resulting in deterioration of workability and characteristics, and if it exceeds 10 at%, it is difficult to obtain sufficient shape memory characteristics. The effect of addition of Sn and Sc was also set in a remarkable range, and in particular, since Sc is extremely expensive, the effect was limited to a sufficient range. Further, the aging condition is limited to a condition that does not affect the increase in hardness.

更に、本合金には、範囲限定外のSn,Sc添加のみならず、また他β安定化元素(Nb、Hf…)或いはα安定化元素(Ag,Al….)を数at％含むことができる。   Further, the present alloy may contain not only Sn and Sc addition outside the range limitation, but also other β stabilizing elements (Nb, Hf...) Or α stabilizing elements (Ag, Al. it can.

・Ti-Nb-Sc系合金
Nbを15〜30at％としたのは、15at％未満および30at％を超えると十分な形状記憶特性が得難くなるためである。Scについてもその添加効果が顕著な範囲とした。また、時効条件限定は前記同様に硬度の上昇影響を及ぼさない条件としたためである。 ・ Ti-Nb-Sc alloy
The reason why Nb is set to 15 to 30 at% is that sufficient shape memory characteristics are difficult to obtain when it is less than 15 at% and exceeds 30 at%. The effect of addition of Sc was also in a remarkable range. Further, the limitation of the aging condition is that the hardness is not affected as in the above case.

更に、本合金には、他β安定化元素(Mo、Hf…)或いはα安定化元素(Sn,Ag,Al….)を数at％含むこともできる。   Furthermore, the present alloy may contain several at% of other β-stabilizing elements (Mo, Hf...) Or α-stabilizing elements (Sn, Ag, Al...).

本発明のTi基合金によれば、少なくとも２％の回復ひずみを有する形状記憶素子が得られ、更にはβ変態温度以上で熱処理した後時効することで３％以上の回復ひずみを有する形状記憶効果、或いは２％以上の超弾性を有する形状記憶素子が得られる。本発明素子は、Niフリーの生体材のみならず、メガネフレーム、ゴルフ用品など幅広い用途への展開が可能である。   According to the Ti-based alloy of the present invention, a shape memory element having a recovery strain of at least 2% is obtained, and further, a shape memory effect having a recovery strain of 3% or more by aging after heat treatment at a β transformation temperature or higher. Alternatively, a shape memory element having superelasticity of 2% or more can be obtained. The element of the present invention can be used not only for Ni-free biomaterials but also for a wide range of applications such as eyeglass frames and golf equipment.

まず、本発明について更に詳しく説明する。   First, the present invention will be described in more detail.

本発明では、生体適合性に優れた合金に着目し、毒性が指摘されているV、Ni、Coなどを除き、毒性またはアレルギー性の指摘がされていないMo、Sn、NbおよびScを少なくとも２種含むTi基合金を用いている。   In the present invention, paying attention to an alloy excellent in biocompatibility, at least 2 Mo, Sn, Nb, and Sc that are not indicated to be toxic or allergenic, except for V, Ni, Co, etc., which are indicated to be toxic. A Ti-based alloy containing seeds is used.

また、本発明では、ベータ型Ti合金と同等な結晶構造を有し、かつ、形状記憶効果若しくは超弾性を有するTi基合金を提供するものである。   In addition, the present invention provides a Ti-based alloy having a crystal structure equivalent to that of a beta-type Ti alloy and having a shape memory effect or superelasticity.

したがって、本発明の対象となるTi合金はチタン合金の中でも加工性が優れたβ型もしくはnearβ型Ti合金である。   Therefore, the Ti alloy that is the subject of the present invention is a β-type or near β-type Ti alloy having excellent workability among titanium alloys.

即ち、本発明においては、Ti合金中に含まれる元素は、毒性の指摘がなく、生体適合性が良い元素として、Mo、Sn、Nb、Scを選択している。   That is, in the present invention, the elements contained in the Ti alloy are Mo, Sn, Nb, and Sc as elements having no indication of toxicity and good biocompatibility.

(1)合金の作製
まず、表１、表２に示すようにβ型あるいはnearβ型となり得る合金組成を選択し、アルゴンアーク溶解によって作製した。溶解はアルゴン雰囲気中で水冷銅ハースと非消耗型タングステン電極を用いたアーク溶解炉で行った。合金成分の偏析を少なくするため、インゴットの天地を逆転させ溶解、凝固を6回繰り返し行った。 (1) Production of Alloy First, as shown in Tables 1 and 2, an alloy composition that can be β-type or near β-type was selected and produced by argon arc melting. Melting was performed in an arc melting furnace using a water-cooled copper hearth and a non-consumable tungsten electrode in an argon atmosphere. In order to reduce the segregation of the alloy components, the ingot was turned upside down and melted and solidified repeatedly 6 times.

作製したインゴットは真空雰囲気中で1000℃×24時間の均質化処理を行い、炉冷した。   The produced ingot was homogenized at 1000 ° C. for 24 hours in a vacuum atmosphere and cooled in the furnace.

(2)試料作製
次に、前述の均質化インゴットから厚さ2〜3mmの板材を切り出し後、0.3〜0.5mmまで圧延した。その後、各試料の一部を１０００℃で１時間熱処理を行い、氷塩水中に焼入れβ単相化処理を行った。 (2) Sample preparation Next, a plate material having a thickness of 2 to 3 mm was cut out from the above-mentioned homogenized ingot and then rolled to 0.3 to 0.5 mm. Thereafter, a part of each sample was heat-treated at 1000 ° C. for 1 hour, and quenched into ice-salt water for β-single-phase treatment.

(3)形状記憶特性評価
特性評価は、上記記載の試験片を用いて簡易曲げ試験によった。まず、厚さ0.3〜0.5mmの板材を半径3〜4mmの円柱に巻きつけた。このとき加えた歪みは、約４〜５%である。その後、巻きつけ開放とライター加熱を行った。形状記憶特性は、巻きつけ拘束解放後のスプリングバック(超弾性)と加熱による残留歪み解消(形状記憶効果)の合量によって評価し、２％以上の回復量を良（表中では○）、１〜２％を普(表中では△)とした。 (3) Shape memory characteristic evaluation The characteristic evaluation was performed by a simple bending test using the test piece described above. First, a plate material having a thickness of 0.3 to 0.5 mm was wound around a cylinder having a radius of 3 to 4 mm. The strain applied at this time is about 4 to 5%. Then, winding release and lighter heating were performed. The shape memory characteristics are evaluated by the total amount of springback (superelasticity) after releasing the winding restraint and residual strain elimination (shape memory effect) by heating, and a recovery amount of 2% or more is good (○ in the table). 1-2% was regarded as ordinary (△ in the table).

(4)時効特性評価
表１，２中の1000℃β化処理した試料を１００℃~７００℃で各５分の時効処理を行い、その形状記憶特性を評価した。評価は前記方法に準じて行った。結果の一例を表３に示す。 (4) Evaluation of aging characteristics Samples subjected to β-treatment at 1000 ° C in Tables 1 and 2 were subjected to aging treatment at 100 ° C to 700 ° C for 5 minutes each, and the shape memory characteristics were evaluated. The evaluation was performed according to the above method. An example of the results is shown in Table 3.

(5)形状記憶効果と超弾性
・Ti-Mo-Sn系合金
図１にTi--5Mo-（3〜6）Sn at％合金の1000℃処理後の特性評価結果を示した。ここにεd：変形与歪、εs：スプリングバック(超弾性)後の残留歪、εr：加熱(形状記憶効果)後の残留歪をそれぞれ表す。 (5) Shape memory effect and superelasticity / Ti-Mo-Sn alloy Fig. 1 shows the results of characterization of Ti--5Mo- (3-6) Snat% alloy after 1000 ° C treatment. Here, εd: deformation strain, εs: residual strain after springback (superelasticity), εr: residual strain after heating (shape memory effect), respectively.

図１に示す結果から、低Sn含有合金は形状記憶効果を示し易く、超弾性は5Snで最大値を示し、6Snではいずれの特性も悪くなることが解る。   From the results shown in FIG. 1, it can be seen that the low Sn content alloy tends to show a shape memory effect, the superelasticity shows a maximum value at 5Sn, and all the properties deteriorate at 6Sn.

また、Moの場合、低Moは合金のβ安定化を十分にすることができず、溶体化時あるいは時効時にω相生成を招き加工性に難点を残す。一方、高Moはβ安定化を十分図ることはできるが、２％以上の形状記憶特性を保持し難くなる。   In addition, in the case of Mo, low Mo cannot sufficiently stabilize β of the alloy, which causes ω phase formation at the time of solution treatment or aging, leaving a difficulty in workability. On the other hand, high Mo can sufficiently stabilize β, but it becomes difficult to maintain shape memory characteristics of 2% or more.

図２にTi-5Mo-5Sn合金の時効温度による材料硬度の関係を示す。図２から、時効効果が得られ易い５分（３００sec.）保持の場合、５００℃未満では硬度の顕著な上昇が見られ、特性劣化を招くことが解る。   Fig. 2 shows the relationship of the material hardness according to the aging temperature of Ti-5Mo-5Sn alloy. From FIG. 2, it is understood that in the case of holding for 5 minutes (300 sec.) Where an aging effect is easily obtained, the hardness is significantly increased at less than 500 ° C., leading to deterioration of characteristics.

図３(a)および(b)に、それぞれ、Ti-5Mo-4Sn合金およびTi-5Mo-5Sn合金の６００℃、５分時効処理材の評価結果を示す。図３から、時効による顕著な特性変化および改善が見られることが解る。   FIGS. 3 (a) and 3 (b) show the evaluation results of the Ti-5Mo-4Sn alloy and Ti-5Mo-5Sn alloy at 600 ° C. for 5 minutes, respectively. It can be seen from FIG. 3 that there is a marked change in characteristics and improvement due to aging.

・Ti-Mo-Sc合金
図４にTi-6Mo−Sc合金のSc濃度変化に伴う形状回復特性を示す。図４から、Sc１at％以下ではその添加効果は小さく、８at％を越えた添加は特性を阻害することが解る。 ・ Ti-Mo-Sc alloy Fig. 4 shows the shape recovery characteristics of the Ti-6Mo-Sc alloy as the Sc concentration changes. From FIG. 4, it can be seen that the effect of addition is small when Sc1 at% or less, and the addition exceeding 8 at% inhibits the characteristics.

図５にTi-Mo-7Sc合金の材料硬度に及ぼす時効条件の影響を示す。前述した図２の場合と異なり200℃に於いても硬度の上昇は認められず、幅広い条件設定が可能であることが解る。   Fig. 5 shows the effect of aging conditions on the material hardness of Ti-Mo-7Sc alloy. Unlike the case of FIG. 2 described above, no increase in hardness is observed even at 200 ° C., and it is understood that a wide range of conditions can be set.

・Ti-Nb-Sc合金
図６にTi-6Sc-(18〜24)Nbat％合金のβ化処理上がりの特性評価結果を示す。図６より低Nb含有合金が形状記憶効果傾向を示すことが解る。 -Ti-Nb-Sc alloy Fig. 6 shows the results of evaluation of the properties of Ti-6Sc- (18-24) Nbat% alloy after β treatment. It can be seen from FIG. 6 that the low Nb-containing alloy shows a shape memory effect tendency.

また、図７にTi-6Sc-26Nb合金の６００℃、７分時効処理の結果を示す。図７から、時効によって超弾性特性が改善されていることが解る。   FIG. 7 shows the result of aging treatment at 600 ° C. for 7 minutes for the Ti-6Sc-26Nb alloy. It can be seen from FIG. 7 that the superelastic characteristics are improved by aging.

図８にTi-6Sc-26Nb合金の材料硬度に及ぼす時効条件の影響を示す。図８から、前述した図２の場合と同様に、５００℃未満での顕著な硬度上昇が認められる。   FIG. 8 shows the effect of aging conditions on the material hardness of Ti-6Sc-26Nb alloy. From FIG. 8, as in the case of FIG. 2 described above, a significant increase in hardness is observed below 500 ° C.

Ti−５Mo−(３〜６)Snat％合金の1000℃処理後の形状記憶特性評価結果を示す図である。It is a figure which shows the shape memory characteristic evaluation result after 1000 degreeC process of Ti-5Mo- (3-6) Snat% alloy. Ti-５Mo-5Sn合金の時効温度による材料硬度の関係を示す図である。It is a figure which shows the relationship of the material hardness by the aging temperature of Ti-5Mo-5Sn alloy. Ti-５Mo-(４,5)Sn合金の６００℃、５分時効処理材の評価結果を示す図である。It is a figure which shows the evaluation result of a 600 degreeC 5 minute aging treatment material of a Ti-5Mo- (4,5) Sn alloy. Ti-6Mo−Sc合金のSc濃度変化に伴う形状回復特性評価結果を示す図である。It is a figure which shows the shape recovery characteristic evaluation result accompanying the Sc density | concentration change of Ti-6Mo-Sc alloy. Ti-Mo-7Sc合金の材料硬度に及ぼす時効条件の影響を示す図である。It is a figure which shows the influence of the aging conditions on the material hardness of Ti-Mo-7Sc alloy. Ti-6Sc-(18〜24)Nbat％合金のβ化処理上がりの特性評価結果を示す図である。It is a figure which shows the characteristic evaluation result after the beta-izing process of Ti-6Sc- (18-24) Nbat% alloy. Ti-6Sc-26Nb合金の６００℃、種々の時間における時効処理材の特性評価結果を示す図である。It is a figure which shows the characteristic evaluation result of the aging treatment material in 600 degreeC and various time of a Ti-6Sc-26Nb alloy. Ti-6Sc-26Nb合金の材料硬度に及ぼす時効条件の関係を示す図である。It is a figure which shows the relationship of the aging conditions exerted on the material hardness of Ti-6Sc-26Nb alloy.

Claims (5)

Moを４〜１０at％含み、Snを３〜１０at%若しくはScを１〜１０at%含み、残部がTiおよび不可避不純物からなることを特徴とするTi基合金形状記憶素子。   A Ti-based alloy shape memory element comprising 4 to 10 at% of Mo, 3 to 10 at% of Sn or 1 to 10 at% of Sc, and the balance comprising Ti and inevitable impurities. Moを４〜１０at％およびSnを３〜１０at%含み、残部がTiおよび不可避不純物からなるTi合金であって、β変態温度以上での熱処理後５００℃以上の温度で時効処理を行ったTi基合金形状記憶素子。   Ti base containing 4 to 10 at% Mo and 3 to 10 at% Sn, the balance being Ti and inevitable impurities, and aging treatment at a temperature of 500 ° C. or higher after heat treatment at or above the β transformation temperature Alloy shape memory element. Moを４〜１０at％およびScを１〜１０at%含み、残部がTiおよび不可避不純物からなるTi合金であって、β変態温度以上での熱処理後１５０℃以上の温度で時効処理を行ったTi基合金形状記憶素子。   Ti base containing 4 to 10 at% Mo and 1 to 10 at% Sc, the balance being Ti and inevitable impurities, and aging treatment at a temperature of 150 ° C. or higher after heat treatment at or above the β transformation temperature Alloy shape memory element. Nbを１５〜３０at%およびScを１at％以上含み、残部がTiおよび不可避不純物からなることを特徴とするTi基合金形状記憶素子。   A Ti-based alloy shape memory element comprising 15 to 30 at% of Nb and 1 at% or more of Sc, the balance being made of Ti and inevitable impurities. Nbを１５〜３０at%およびScを１at％以上含み、残部がTiおよび不可避不純物からなるTi合金であって、β変態温度以上での熱処理後５００℃以上の温度で時効処理を行ったTi基合金形状記憶素子。

Ti-base alloy containing 15-30at% Nb and 1at% or more of Sc, the balance being Ti and inevitable impurities, and aging treatment at a temperature of 500 ° C or higher after heat treatment at a β transformation temperature or higher Shape memory element.