Microstructure And Mechanical Properties Evolution Of ATZ331 Alloy During Accumulative Roll-bonding

Magnesium alloys are promising structural materials due to their excellent properties,such as low density,high specific strength and specific stiffness,as well as machinability and recyclability.However,the poor ductility limited its industry utilized,grain refinement is the most effective measure to improving the ductility and strength of magnesium alloy.Accumulative roll-bonding is a severe plastic deformation technique which can improve the synthesis mechanical properties of magnesium alloy effectively.In the accumulative roll-bonding process,material can be repeated rolling,equivalent strain can reach a larger value,a larger amount of reduction than the traditional rolling.The ultrafine grained magnesium alloy sheets can be continuously produced.In this study,we fabricated the ATZ331 alloy ingot by the gravity casting in the permanent mold.The microstructures of the ATZ331 alloy in the as-cast,as-soluted,as-rolled and accumulative roll-bonding state were characterized,the mechanical properties of ATZ331 alloy were tested and the factors of dynamic recrystallization,precipitation particles,twins,equivalent strain,texture which effect the microstructure and mechanical properties of ATZ331 alloy were analysed.The main results are as follows:(1)The spherical phase of Mg2Sn distributed on the grain boundary in the as-cast ATZ331 alloy.The ultimate tensile strength and elongation of as-cast ATZ331 alloy is 216.5MPa and 16.8%,respectively.(2)The precipitation are dissolved into a-Mg matrix when the ATZ331 alloy soluted with the process of 415?×16h+450?×8h,which achieved the solid solution strengthen of ATZ331 alloy.The ultimate tensile strength and elongation of as-soluted ATZ331 alloy is 227MPa and 21.62%,respectively.However,the microhardness of as-soluted ATZ331 alloy is slightly lower.(3)The microstructure and mechanical properties of as-rolled ATZ331 alloy is researched,with the different hot rolling processes,the best hot rolling process has been optimized:in the rolling process of R-300?-10%-80%,along the longitudinal direction of the rolled sample,the ultimate tensile strength and elongation of as-rolled ATZ331 alloy is 298MPa and 9.9%,respectively;along the transverse direction of the rolled sample,the ultimate strength and elongation of as-rolled ATZ331 alloy is 343MPa and 20.5%,respectively;the ultimate tensile strength and elongation of cross rolling ATZ331 alloy is 328MPa and 18.6%,respectively.In the rolling process of R-400?-20%-80%,along the longitudinal direction of the rolled sample,the ultimate tensile strength and elongation of as-rolled ATZ331 alloy is 285MPa and 18.3%,respectively;along the transverse direction of the rolled sample,the ultimate strength and elongation of as-rolled ATZ331 alloy is 308MPa and 22.4%,respectively;the ultimate tensile strength and elongation of cross rolling ATZ331 alloy is 294MPa and 19.7%,respectively.Dynamic recrystallization refines grain effectively,fine dispersed spherality precipitation of Mg2Sn distributed in all over of the substrate which are useful of increasing strength and preventing grain growth.(4)The 1.3mm plates of R-400?-20%ATZ331 alloy in the process of ARB-300?20min+400?10min for 3 cycles,the average grain size,ultimate tensile strength and elongation of ARBed ATZ331 alloy is 1.67?m,421MPa,8.76%,respectively;The 1.3mm plates of R-400?-20%ATZ331 alloy in the process of ARB-400 ?10min for 4 cycles,the average grain size,ultimate tensile strength and elongation of ARBed ATZ331 alloy is 1.80?m,357 MPa,7.69%,respectively;The 1.3mm plates of R-300?-10%ATZ331 alloy in the process of ARB-400 ?10min for 4 cycles,the property of ARB3 is the best,the average grain size,ultimate tensile and elongation of ARBed ATZ331 alloy is 1.55?m,317MPa,15.8%,respectively.The changes in tensile strength and ductility are more complicated as a result of the combined effects of the temperature and equivalent strain on grain size,texture and interface bonding.