Microstructures in an Fe Based Shape Memory Alloy and Al Based Dual Phase Crystals after High Speed Deformation

Abstract

Microstructures have been examined after high-speed deformation given by free weight drop and air gun shooting. Special care was exercised to control the amount of plastic strain so that the deformed specimen could be examined as a function of total plastic strain as well as strain rate. Al based dual phase alloys of Al-Al 3 Fe, Al-Al 3 Ti and Al-Al 3 Ni have been examined both at slow and high-speed strain rates using sheet specimens of various thickness, in order to find strain rate effects on the deformability of the ordered second phase particles embedded in Al. The ordered phases, not deformable at a low strain rate in the Al based alloys, are shown to be deformed by dislocation glide in the high strain rate tests. The another aspect of the study is concerned with the mechanical and structural changes in Fe-Mn-Si based shape memory alloys by high-speed deformation. The shape recovery under the opposing stress is found to increase notably after the shape deformation given by shock loading. Also, the effect of shock loading was examined using a thin foil specimen prepared for electron microscopy. In these tests, thin foil regions were locally amorphized presumably by the heavy shear deformation induced at high strain rate.