Functionally gradient microstructure in Ti-Al-Cr (L1_0/L1_2) alloys under impact ultra-high pressure

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 12650704
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Structural/Functional materials
• Research Institution: Niihama National College of Technology
• Principal Investigator: TAKAHASHI Tomoshi Department Mater. Eng. Professor, 材料工学科, 教授 (30110159)
• Co-Investigator(Kenkyū-buntansha): MINAMINO Yoritoshi Graduate School, Osaka University, 大学院・工学研究科応用理工学系, 教授 (30116107) ; SHIGA Shinya Niihama National College of Technology, Associate Professor, 材料工学科, 助教授 (60235512)
• Project Period (FY): 2000 – 2002
• Keywords: Ti-Al-Cr alloy system / Ultra-impact high pressure / L1_2 structure / Interdiffusion / Functionally gradient microstructure

Research Abstract

The interdiffusion experiments and the formation experiments of gradient microstructure have been performed in a temperature range from 1273 to 1573 K by using the diffusion couples of Ti/Ti-Al-Cr, Ti-Al/Ti-Cr and Ti-Al-Cr (Ll1_0) /TrAl-Cr (L1_2) alloys. Furthermore, the high-speed impact deformation experiments have been carried out in the above Ti alloys. (1)The gradient microstructure have been observed in each temperature. In the Ti/Ti-Al-Cr couples, the martensitic structure are formed near the Matano interface. The alloy couples soften at the composition hi the terminal alloy side, because of the formation of retained β phase.
(2)The concentration profiles indicate that the diffusion distance of Cr is longer than that of Al in the solid solutions. The diffusion paths S-shaped curves. The binary and ternary interdiffusion coefficients are not sensitive to the solute concentrations.
(3)The change in microstructure and hardness of Ti-38.1Al-4.8Cr (L1_0) alloys depend on cooling rate after the heat treatment at 1473 K for 24 h.