Study On The Microstructure And Mechanical Properties Of Mg-Zn-Al-(Y) Alloys Reinforced With Quasicrystals

Quasicrystalline phase can effectively improve mechanical properties of magnesium alloys at both room temperature and elevated temperature, due to its high hardness and strength and strong combination with Mg matrix. Quasicrysal is also effective to weaken extrusion textures and yield strength asymmetry.Microstructures and mechanical properties of both as-cast and extruded Mg-Zn-Al-(Y) alloys were investigated. The relationship between flow stress and strain rate of ZA84 and ZAY8405 alloys during hot compression deformation was studied. Textures and yield strength asymmetry of ZA84 and ZAY8405 alloys were also discussed.Mg-Zn-Al-(Y) alloys contained i-phase as a main strengthening phase. The 0.5 at.% Y addition was effective for decreasing the size of i-phase and the increasing the homogeneity of its dispersed state. Deformation twinning and dynamic recrystalization during hot compression are easier to take place, due to the high symmetry of quasicrystal and its definite orientation relationship with -Mg matrix.The quasicrystal phase is dispersed as particles in the matrix after hot extrusion at 230℃, with an extrusion ratio of 10. Mechanical properties of Mg-Zn-Al-(Y) alloys were further improved. Ultimate tensile strength, yield strength and elongation of as-extruded ZA84 alloy were 178MPa,300MPa and 16.0%, wich of ZAY8405 alloy were 178MPa,321MPa and 19.3%.Quasicrystalline phase dispersed in the matrix during hot-extrusion can activate non-basl slip and relatively random textures were found in as-extruded ZA84 and ZAY8405 alloys. Yield strength asymmetry of ZA84 and ZAY8405 alloys were also weakened compared with AZ31 alloys.