Design and experimental investigation of the high-entropy alloys AlCrFeNiCu and AlCrFeNbMo

To improve the service safety of accident-tolerant fuels in nuclear power plants, the high-entropy alloys (HEAs) AlCrFeNiCu and AlCrFeNbMo were designed and prepared through mechanical alloying (MA) and spark plasma sintering (SPS) processes in this work. The phase structures of AlCrFeNiCu and AlCrFeNbMo were predicted and verified. The microstructure, phase structure, and properties of alloy powders and sintered alloy were investigated under various ball-milling conditions. Results show that the phase formation rule of HEA is an empirical criterion that still needs experimental verification. The HEA powder was refined and had good fluidity after MA. Body-centered cubic (BCC) AlCrFeNbMo powder can be prepared at high milling speeds and long milling times, while the structure of AlCrFeNiCu powder was a BCC plus face-centered cubic (FCC) duplex phase structure. The spark plasma-sintered alloy had fine grains (<1 μm) and a multiphase structure. AlCrFeNiCu was mainly composed of FCC, B2, and a trace of σ phase, while AlCrFeNbMo was composed of BCC, FCC, and σ phase. The density, hardness, compressive strength, yield strength and strain of AlCrFeNiCu and AlCrFeNbMo alloys were 6.54 g cm-3, 447.57 HV, 1727 MPa, 1642MPa and 15% and 6.32 g cm-3,1188.82 HV, 2183MPa, 1943MPa, and 19%, respectively, which are higher than reported for most HEAs that were prepared by SPS. The fracture mechanism is the typical brittle fracture. Because of solution strengthening and precipitation strengthening, AlCrFeNiCu and AlCrFeNbMo have excellent mechanical properties.