The microstructure and thermomechanical behavior of Ti50Ni47Fe2.5Nd0.5 shape memory alloys

This work presents a study of a novel Ti50Ni47Fe2.5Nd0.5 shape memory alloy by EPMA, E-R analysis and tensile tests. Structural characterization shows the alloy consists of TiNiFe matrix, Nd3Ni and Ti2Ni intermetallic compounds with Fe solute. The latter two phases are well distributed in the matrix. Compared with Ti50Ni47.5Fe2.5 alloys without rare earth Nd, the novel alloy does not change the two-stage martensitic transformation behavior, however, characteristic temperatures increase rapidly. The critical stress needed for inducing martensitic transformation is near linear relationship with the increasing of the testing temperature above Ms, which is in good agreement with Clausius-Clapeyron equation. The novel alloy exhibits an improved shape memory effect as a consequence of precipitation strengthening and the maximum recoverable strain attains to 7.8%.