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

利用Ti/Ti- al - cr、Ti- al /Ti- cr和Ti- al - cr (Ll1_0) /TrAl-Cr （L1_2）合金的扩散偶，在1273 ~ 1573 K的温度范围内进行了相互扩散实验和梯度组织的形成实验。此外，还对上述钛合金进行了高速冲击变形试验。(1)在各温度下均观察到梯度组织。在Ti/Ti- al - cr对中，马氏体结构在Matano界面附近形成。由于残留β相的形成，合金偶在末端合金侧的成分处软化。(2)浓度分布表明，Cr在固溶体中的扩散距离大于Al。扩散路径呈s形曲线。二元和三元扩散系数对溶质浓度不敏感。(3) 1473 K热处理24 h后，Ti-38.1Al-4.8Cr （L1_0）合金显微组织和硬度的变化与冷却速率有关。

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.