Ti-15V-3Cr-3Sn-3Al系合金の強靭性におよぼすβ粒径と時効組織の影響

抄録

Effects of beta grain size and aged microstructure on mechanical properties have been investigated for a Ti-15V-3Cr-3Sn-3Al based alloy.
The beta grain size linearly increases with increasing solution treatment temperature. With increasing solution treatment temperature from 1023 to 1173 K, the 0.2% yield strength in the solution treated condition decreases in accordance with Hall-Petch relationship. The 0.2% yield strength of the specimens aged at 773 K for 28.8 ks indicates an approximately constant value of 1100 MPa, independently of the grain size. The elongation and reduction in area are strongly dependent on grain size and decrease with increasing grain size. The notched tensile strength is independent of the grain size, while, K_IC slightly increases with increasing grain size. Unusual age-hardening behavior exhibiting two hardness peaks at 623 and 723 K for 28.8 ks can be observed. These two peaks indicate the same values of hadness and tensile strength. However, the specimen aged at 623 K shows both poor ductility and notched tensile strength, compared to the higher temperature aged structure, due to fine and coherent α precipitation in beta matrix.