Dual phase equal-atomic NbTaTiZr high-entropy alloy with ultra-fine grain and excellent mechanical properties fabricated by spark plasma sintering

Abstract Super-high strength NbTaTiZr high-entropy alloys (NbTaTiZr HEAs) have been successfully fabricated by the mechanical alloying (MA) with spark plasma sintering (SPS) technology, which is 2-fold compared with that of NbTaTiZr HEAs prepared by vacuum arc melting (VAM). After the SPS process, the bulk NbTaTiZr alloy samples are provided with dual-phase body-centered cubic (BCC) structure and nanoscale grain size about 500 nm that is obviously smaller than that of NbTaTiZr HEA fabricated by VAM. When the sintering temperature is 800 °C, the compressive fracture strength is the highest reaching at 2511 ± 78 MPa. When the sintering temperature is 1000 °C, the fracture strain is the highest reaching at 12.8%, and compressive fracture strength and yield strength also reach at 2274 ± 91 MPa and 2172 ± 47 MPa, respectively. The excellent mechanical properties of bulk NbTaTiZr alloy samples are attributed to the merits of MA and SPS, and the collaboration effect of ultra-fine grains strengthening, solid solution strengthening and interstitial solid solution strengthening.