Novel Al-Sc-Ti-Zr multi-principal element alloys with outstanding mechanical properties

Non-equiatomic multi -principal element alloys, namely Al5Sc25Ti35Zr35, Al10Sc20Ti35Zr35 and Al15Sc15Ti35Zr35, with a density of approximately 4.95 x 103 kg/m3, were prepared by casting and subsequently treated with dualannealing. The microstructure and compressive mechanical properties of both the as -cast and annealed samples were investigated at room temperature, while the mechanical properties of those with good performance were also studied at 873 K. In the as -cast Al5Sc25Ti35Zr35 alloy, a single hcp phase was formed, while dual hcp phases were observed in the annealed state. With an increase in Al content, the amount of the bcc phase increased. The compressive strength initially decreased and then increased for the as -cast samples, whereas it consistently decreased for the annealed ones. Among all the tested samples, the Al15Sc15Ti35Zr35 alloy demonstrated the most outstanding mechanical properties, achieving a high compressive strength of 2584 MPa at a strain of 31.9% at room temperature, and a strength of 804 MPa with a strain exceeding 50% at 873 K. Regarding the other hcpcontaining alloys, the Al5Sc25Ti35Zr35 alloy with a dual-hcp structure exhibited a high strength of 2040 MPa at a strain of 14.9% and a strength of 692 MPa with a strain of 45% at 873 K. The underlying reasons for the differences in mechanical properties were thoroughly discussed. This research provides valuable insights into the development of the lightweight multi -principal element alloys containing hcp or bcc phase, which exhibit outstanding properties for future applications as structural materials.