Effects of ECAE process on microstructure and transformation behavior of TiNi shape memory alloy

Equal channel angular extrusion (ECAE) process was a deep pure shear deformation method for structural materials, developed in early 90s. ECAE technique has been successfully applied to several pure metals and alloys to refine the microstructure and improve the mechanical properties of materials. In the present paper, TiNi shape memory alloys have been treated by ECAE process. The effects of ECAE process on microstructures and transformation behaviors have been investigated. The initial coarse grains of TiNi alloy were refined after two passes of ECAE processes and short annealing at 1023 K. Transformation temperatures of TiNi alloy sharply decreased after two ECAE processes, then rapidly rose back when annealed at 773 K for 2 h.