Effect of Re on the microstructure and mechanical properties of NbTiZr and TaTiZr equiatomic alloys

Overview & Synopsis

The microstructure, phase composition, and mechanical properties of NbTiZr, TaTiZr, Re$_{0.3}$NbTiZr, and Re$_{0.3}$TaTiZr are reported. The alloys were produced by vacuum arc melting and hot isostatically pressed (HIP’d) at 1400°C for 3 h under 276 MPa hydrostatic pressure of high-purity argon prior to testing. NbTiZr had a single-phase BCC crystal structure, while TaTiZr had a Ti- and Zr-rich BCC matrix phase and Ta-rich nanometer-sized BCC precipitates, at volume fractions of 0.49 and 0.51, respectively. Re$_{0.3}$NbTiZr consisted of a BCC matrix phase and Re-rich precipitates with a FCC crystal structure and the volume fraction of 0.14. The microstructure of Re$_{0.3}$TaTiZr consisted of a Zr-rich BCC matrix phase and coarse, Re and Ta rich, BCC particles, which volume fraction was 0.47. NbTiZr and TaTiZr had a room temperature (RT) yield stress of 920 MPa and 1670 MPa, respectively. While, 10 at.% Re additions increased the RT yield stress to 1220 MPa in Re$_{0.3}$NbTiZr and 1715 MPa in Re0.3TaTiZr. Re also considerably improved the RT ductility of TaTiZr, from about 2.5% to 10% of true strain. The positive strengthening effect from the Re additions was retained at high (800–1200°C) temperatures.