Abstract:The microstructure, martensitic transformation behavior, mechanical and shape memory properties of Ni₅₆Mn_25−xCr_xGa₁₉ (x=0, 2, 4, 6) alloys were investigated. Single phase of martensite with tetragonal structure is present for x=0, and dual-phase containing martensite and γ phase is observed for x≥2. The martensitic transformation peak temperatures decrease monotonically from 401 °C for x=0 to 197 °C for x=6. The introduction of γ phase by Cr addition is proved to be effective in improving the workability and ductility. The tensile stress and strain are 497 MPa and 8 % for x=4, and 454 MPa and 5.5 % for x=6, respectively. The shape memory strain values are 2.7 % under a residual strain of 4.5 % for x=4, and 1.9 % under a residual strain of 3.5 % for x=6, respectively.

Key words: martensitic transformation; tension; ductility; high-temperature shape-memory effect