QUENCH-HARDENING MECHANISM BASED ON THE ELECTRICAL PROPERTIES IN NON-STOICHIOMETRIC NiTi.

Abstract

To clarify the cause of quench hardening in Ni-rich NiTi, the relation between composition and electric resistivity and the change in electric resistivity at a constant rate of heating were investigated. The analysis of the results of the electric resistivity measurements indicates that the ordered NiTi phase is stable but has a restricted homogeneity range at low temperatures, the precipitation of Ni//3Ti in the water quenched state is hardly conceivable, and the existence of the order-disorder tansformation and the eutectoid reaction is improbable. It is concluded that quench hardening in nonstoichiometric NiTi is due to quenched-in defect structures.