集合組織に基づくγ-TiAl金属間化合物における動的再結晶機構の解析

Abstract

Uniaxial compression tests were conducted on the Ti-52 mol%Al intermetallic compound at the temperatures and strain rates ranging from 1173 to 1473 K and 4.0×10−5 to 5.0×10−3 s−1, respectively. The mechanism of dynamic recrystallization of the compound was examined on the basis of texture analysis. A fiber texture was formed during dynamic recrystallization. The main component of the texture is given approximately by (032) (compression plane) irrespective of the deformation temperatures, strain rates and strains. The sharpness of the texture varies depending on strains and the peak stresses appearing in the true stress-true strain curves. Thus the texture formation should be attributed to the deformation process; the recrystallization process has an effect of changing the texture sharpness. One to one correspondence exists between the texture sharpness and the peak stresses when the texture sharpness is evaluated at true strains about −1.7. When the peak stress is low, the texture sharpens monotonously with increasing strain, whereas the textures at high peak stresses stop developing at the strains more than −1.0. These results suggest that the dynamic recrystallization proceeds by the mechanism succeeding to the formation of the texture by crystal slip at low peak stress conditions and the mechanism at high peak stress disturbs the texture development. The existence of the two different mechanisms which have been proposed by microstructural observation, namely strain induced grain boundary migration and the nucleation and growth mechanism, are elucidated by the texture analysis.