Effects of temperature and loading direction on deformation mechanism of Ti-10at%Al alloy subjected to rolling and high speed compression

Abstract

In this paper, Ti-10at%Al alloy samples were subjected to rolling and high speed compression under different temperatures and along different loading directions (the transverse direction (TD) and normal direction (ND) of the pre-rolled samples), to explore the effects of temperature and loading direction on the deformation mechanisms.101̅2 and 112̅1 twins were activated in all these deformed specimens. 112̅1 twins prevailed in both the room temperature rolled and liquid nitrogen rolled specimens but were severely inhibited during hot rolling, while 101̅2 twins did not show obvious change with the temperature. Planar slip of dislocations occurred during room temperature rolling and liquid nitrogen rolling, while cross slip occurred during hot rolling. The change of dislocation behaviors at different temperatures may be caused by the variation in stacking fault energy as an effect of temperature. Moreover, the number of twins in the deformed samples along TD was always higher than that along ND both under rolling and high speed compression. When loaded along TD, most of the grains were with or close to the orientations of<21̅1̅0> and<101̅0> , which were favorable for the activation of 101̅2 and 112̅1 twins. Therefore twinning played a significant role when loaded along TD, while dislocation slip dominated the deformation when loaded along ND. The hardness increased after deformation under different conditions, and the hardness of specimens after rolling or compression along ND was generally higher than that along TD due to the reason that most of the grains were in the hard< 0001 > orientation when loaded along ND, activation of<c+a> dislocations on pyramidal planes with high critical resolved shear stress was required.