Strain rate sensitivity and deformation activation volume of coarse-grained and ultrafine-grained TiNi alloys

Two TiNi alloys, Ti49.4Ni50.6 and Ti50Ni50, are subjected to equal-channel angular pressing (ECAP) resulting in the formation of a homogeneous ultra-fine grained microstructure. Tensile tests and strain rate jump tests are carried out in the temperature range of 25-400 °C to measure mechanical properties and strain rate sensitivity of both alloys before and after ECAP processing. Effect of grain size on mechanical behavior, strain rate sensitivity and mechanisms operating during plastic deformation of both alloys in the given temperature range is discussed.