冷間圧延したTi-20V-4Al-1Sn合金における圧下率と組織形態および機械的性質との関係

摘要

This study was conducted to investigate the relationship of rolling reduction with the microstructure and mechanical properties of cold-rolled Ti-20V-4Al-1Sn alloy. Cold rolling was performed under the rolling reduction between 10-50%. The micro-structure was compressed by cold rolling, and became finer. Plastic deformation was partially inhomogeneous in the thickness direction of the cold-rolled material. The preferred orientation of the formed crystallographic texture was {112}<110>〜 {001}<110> which is typical in metals possessing the bcc structure. The texture evolved with increasing rolling reduction. Hardness and static strength were increased by increase in rolling reduction because of work hardening and microstructural refinement. Anisotropy was induced in yield strength and work hardening exponent by cold rolling; however, it was not marked in hardness and tensile strength.%チタンは比強度が高く，また耐食性に優れていることから，航空宇宙産業や生体医療分野を中心に広く使用されている.しかしながら，代表的なα+β型チタン合金であるTi-6Al-4V合金等はhcp構造を有するα相を含むため，冷間加工性に劣っている.このような背景から，Ti-15V-3Cr-3Sn-3Al合金やTi-20V-4Al-1Sn合金などのβ型チタン合金が開発されている.β型チタン合金は，VおよびCr等のβ安定化元素を比較的多量に含有し，溶体化処理によりβ単相(bcc構造)とすることで優れた変形能を示す.さらに時効処理を施せば，Ti-6A1-4V合金等のα+β型チタン合金を超える水準まで高強度化することが可能である.