Phase Decomposition and Elevated Temperature Mechanical Properties of Zr–Ti–Nb–Ta–Sn Complex Concentrated Alloy Annealed at Intermediate Temperatures

Refractory complex concentrated alloys (RCCAs) have attracted much attention due to their unique design concept and mechanical properties at elevated temperatures. The researchers found that the RCCAs are thermally metastable and could decompose in certain temperature ranges. At present, the phase stability of these alloy systems is not completely clear. In this work, the phase stability of single-phase body-centered cubic (BCC) Zr46Ti13Nb26Ta10.5Sn4.5 alloy annealing between 600 °C and 1000 °C was evaluated, and the effects of phase decomposition on high-temperature mechanical properties were studied. Annealing at 1000 °C, it is unstable and forms a second-phase precipitate with BCC structure (termed as BCC2). After annealing at 600 °C to 800 °C, a new Zr–Sn-rich hexagonal-closed-packed (HCP) phase was formed. At high temperatures (1000 °C to 1200 °C), the “fishbone”-shaped GB precipitates can hinder the sliding of GBs and the intragranular precipitates hinder dislocation movement causing a significant increase in strength. These results indicate that the high-temperature mechanical properties of RCCAs can be improved by optimizing the microstructure by tuning the phase stability, which sheds light on designing new RCCAs with high performance.