Study On Microstructure And Mechanical Properties Of Al-Sc-Ti-Zr Multi-principal Elements Alloy

As a new type of multi-principal elements alloy,high entropy alloy has attracted much attention due to its excellent mechanical properties.At present,more researches are focused on the single-phase BCC or FCC structure and dual-phase BCC+FCC structure,while the multi-component alloy with HCP structure is relatively less reported.In this paper,based on the theory of high-entropy alloys,a multi-principal Al-Sc-Ti-Zr alloys which may form HCP structure was designed by qualitative analysis of binary phase diagram and ternary phase diagram,and its microstructure and mechanical properties were analyzed.The following work has been carried out:?1?The isothermal section of Al-Sc-Ti ternary system at 1073 K was measured by alloying method,the solubility of the third component in binary compound was analyzed,and the primary crystalline phase of alloy solidification was determined by analyzing as-cast alloy.?2?The multi-principal elements alloys of Al₁₅Sc₁₅Ti₃₅Z_r35,Al₁₀Sc₂₀Ti₃₅Zr₃₅5 and Al₅Sc₂₅Ti₃₅Zr₃₅5 with unequal atomic ratios were designed by qualitative analysis combining binary phase diagram and four sub-ternary phase diagrams.?3?The microstructure and mechanical properties of as-cast Al-Sc-Ti-Zr alloy were analyzed.It was found that Al₁₅Sc₁₅Ti₃₅Zr₃₅5 alloy was mainly composed of?-BCC phase with a small amount of?+??+?phase,Al₁₀Sc₂₀Ti₃₅Zr₃₅5 was composed of BCC and HCP phases and Al₅Sc₂₅Ti₃₅Zr₃₅5 alloy was composed of a HCP structure.Among them,the Al₁₀Sc₂₀Ti₃₅Zr₃₅5 alloy has the highest compressive strength which up to 1913 MPa,but the Al₁₅Sc₁₅Ti₃₅Zr₃₅5 alloy has the best plasticity up to 14.8%.?4?The microstructure and mechanical properties of heat-treated Al-Sc-Ti-Zr alloy were analyzed.It was found that Al₁₅Sc₁₅Ti₃₅Zr₃₅5 and Al₁₀Sc₂₀Ti₃₅Zr₃₅5 alloy were composed of HCP and BCC phase,and Al₅Sc₂₅Ti₃₅Zr₃₅5 alloy was composed of two kinds of Ti and Sc rich HCP phase.In the heat-treated alloy,the best mechanical property is Al₁₀Sc₂₀Ti₃₅Zr₃₅5 alloy,whose compressive strength reached 2134MPa,and the best plasticity is Al₅Sc₂₅Ti₃₅Zr₃₅5 alloy,whose value is 19%.