Effect of Heat Treatment on the Structure and Microhardness of the Ti₅₀Pd₃₀Ni₂₀ Alloy with a High-Temperature Shape Memory Effect

The structure and microhardness of the Ti₅₀Pd₃₀Ni₂₀ (at %) alloy with a high-temperature shape memory effect have been comprehensively studied. The investigations have been carried out on the alloy samples cut from a 2.09-mm-thick strip in the initial state and after heat treatment under different conditions. Data on the elemental and phase compositions, microstructure, grain size, and microhardness have been obtained. It has been found that the main phase of the Ti₅₀Pd₃₀Ni₂₀ (at %) alloy in the initial state and after heat treatment is a solid solution based on the TiPd (B19) phase in a low-temperature martensitic state with an orthorhombic crystal lattice; Ni is introduced in the TiPd (B19) phase with the formation of a solid solution with it. Heat treatment barely changes the parameters a_exp, b_exp, and c_exp as compared with the initial state; i.e., the crystal lattice distortions caused by defects are minor, and the changes in the crystal lattice parameters a, b, and c as compared with the reference values are caused mainly by the deviation of the alloy composition from the stoichiometric one and by the formation of a solid solution based on the TiPd (B19) phase.