NiTiNb shape memory alloys fabricated via the reactive sintering of elemental powders: Microstructures, transformation behaviors and compressive properties

Abstract

Elemental powder sintering is an important low-cost preparation method for NiTiNb shape memory alloys. Usually, the performance is poor due to high impurity content and macroscopic defects. In this study, high-strength NiTiNb alloys without macroscopic defects were successfully prepared using mixed elemental powders based on the previous investigation. Higher sintering temperature and Nb addition brought about faster atomic diffusion, which strongly affected the densification, grain size, phase composition and Nb solid solution, and further determined the transformation temperature and mechanical properties. The transformation temperature decreased with increasing Nb solid solubility. A high thermal hysteresis of 72–75 °C was obtained by nano-Nb precipitation. The compressive strength reached 1662–2185 MPa. The recovery properties gradually decreased with the increase of large Nb particles in the matrix, which should be optimized in further studies. Overall, the addition of Nb drastically reduced the sintering temperature of elemental NiTi powders, which was conducive to suppressing the loss of liquid phase and promoting homogenization. It provides a new idea for the preparation of high-performance, fully dense and low-cost NiTi-based alloys.