Texture and microstructure of HPT-processed Fe-based shape memory alloys

Texture and microstructure evolution of Fe-based shape memory alloys subjected to high pressure torsion (HPT) at room temperature was investigated using synchrotron radiation and electron backscatter diffraction in the scanning electron microscope. As starting material for HPT a directionally solidified Fe-based alloy characterized by a fiber texture and coarse columnar grains with a mean size of about 300 μm was used. Prior to HPT the samples were quenched and heat treated for precipitation hardening for 24 h at 700°C. HPT-processing changes the initial texture to a typical shear texture with dominating C component. As deformation proceeds an intensive stress-induced precipitation of a brittle NiAl-B2 phase takes place. The precipitates form a typical shear texture of bcc metals with F component dominating. The C and F components may lead to specific interphase orientation relationships