Study On Microstructure And Properties Of Mg-3Al-3Sn-Zn Alloy

Magnesium alloy is known as "the21st century green engineering material" and hasmany excellent unique properties, such as high specific strength, high specific stiffness,conductive thermal conductivity, good damping shock and electromagnetic shieldingperformance, easy processing and forming, good renewable recovery utilization etc,so theapplication is very wide. In recent years, because the energy and environment problems areincreasingly serious, magnesium alloy is researched and attracts more and more attention, andso on the new magnesium alloy system of basic research is of great significance. In thisstay,we prepare the new type of the ATZ331alloy ingot by the gravity casting based on themetal mold and research the as-cast and solution state, rolling state on the microstructure andmechanical properties of the observation.We optimize the solution, rolling processparameters and explore the solution state and rolling state ATZ331alloy fortitude changemechanism.The results show that the microstructure of the ATZ331as-cast alloy is mainlycomposed of α-Mg, Mg17Al12, Mg2Sn and MgZn phase by researching the ATZ331as-castalloy. The matrix of α-Mg is isometric, the Mg17Al12phase of the intermittent networkdistributes in α-Mg grain boundary. The Mg2Sn phase is granular and intermittent network,the granular Mg2Sn phase is mainly in a interdendritic of the α-Mg isometric and theintermittent network Mg2Sn phase also distributes in α-Mg grain boundary.the MgZn phaseis intermittent network and granular,it distributes in α-Mg boundary.The ATZ331alloy hasa good mechanical properties, the best tensile strength is222MPa, the elongation is18%.After researching the microstructure and mechanical properties of the ATZ331alloy bythe different solid solution processing, we found the best solution process is that first in415℃heat preservation16hours, and then temperature to450℃heat preservation8hours. Afterthe above solution process, the ATZ331alloy is mainly composed of a-Mg composition andonly a very small Mg2Sn phase residual. especially the twin is found in the solution stateATZ331alloy microstructure. The mechanical properties of the alloy is best, the tensilestrength reached237MPa, the elongation is21.7%, its strong chemical mechanism is mainlydue to the solid solution strengthening and twin reinforcement, but the solid solution state alloy micro-hardness is slight lower.After researching the microstructure and mechanical properties of the rolling and rollingannealing state ATZ331alloy, we found the best process of the unidirectional and crossrolling in this experiment conditions is that the rolling temperature is400℃, the passreduction is20%, the rolling annealing temperature is300℃and the holding time is1hour.The tensile strength is292MPa and the elongation is25.9%of the One-way rolling stateATZ331alloy. The tensile strength is363MPa, the elongation is15.6%of the transverse ofthe ATZ331alloy. The mechanical properties exist anisotropy, it is mainly due to the {0001}base texture of the ATZ331rolling plate, the {0001} base texture can make the base Schmidfactor increases, the yield strength decreased. The tensile strength is270MPa and theextension rate reaches as high as30.7%after annealing. The tensile strength is274MPa andthe elongation is21.4%of the Cross rolling state ATZ331alloy. Although its tensile strengthand elongation are lower than the unidirectional rolling alloy’s, but the cross rolling alloy’smechanical properties are equilibrium in each direction. The alloy micro-hardness increasesand a rolling precipitated phase exists after rolling.