Study On Microstructure And Mechanical Properties Of Mg - Sn Deformed Magnesium Alloy

As the lightest industrial structure materials, Magnesium alloys have a broad prospect of application with a series of advantages such as low density, high strength ratio, high stiffness ratio, excellent damping capacity, electromagnetic shielding resistance and so on.The Mg-Sn alloys is one of the new type aging strengthening deformation magnesium. As one of the precipitation strengthening elements, the solubility of Sn in α-Mg solid solution drops sharply from 14.85wt% at the eutectic transformation temperature of 561℃to 0.45wt% at 200℃. This provides an important basis for improving the mechanical properties of Mg-Sn alloys through heat-treatment. At the same time the Mg2 Sn phase is a normal valence compound with high hardness of 119 HV and high melting temperature at about 770.5℃. In order to provide some scientific bases for expand the application of Mg-Sn alloys. Comprehensive the above characteristic three kinds of experiments were designed(Mg-xSn(x=1.0, 3.0, 9.0)-1.5Y-0.4Zr) in this article and investigated by optical microscope, scanning electron microscope(with EDS), X-Ray diffraction, Vickers hardness tester, electronic mechanical universal testing machine and other equipments.The results show that: The second phases and finer grains distributed along the extrusion direction in the as-extruded alloy and no casting defects found in it; The hardness and yield strength increased but the elongation was decreased with the content of Sn increased;In contrast with different heat treatment processes, the solid-solution under 495℃/10 h has the remarkable effect.The elongation was highly improved with the strength and hardness of specimens general decreased in some degree.Aging treatment after solid-solution is the most efficient method to improve the mechanical properties of Mg-Sn alloys. The mechanical properties of as-extruded Mg-9Sn-1.5Y-0.4Zr alloy were: 79.5HV(Hardness),174MPa(Yield Strength)and9.7%(Elongation)respectively; After solid-solution the elongation of 9Sn alloy was promoted at about 35.1% contrast with the as-extruded to 13.1%;Aging treatment at 250℃after solid-solution is the most efficient method to improve the mechanical properties of Mg-Sn alloys.The mechanical properties of Mg-9Sn-1.5Y-0.4Zr alloy after aged at 250℃for 60 h were:89HV(Hardness),218MPa(Yield Strength)and 10.4%(Elongation) improved than the as-extruded at about 11.9%, 25.3%, 7.2%, respectively. Calculated through the G-D model, indicating a strong strengthening effect of precipitation strengthening(51.76%) in the aged 9Sn alloy. The fracture morphology indicated that the amounts of dimples increased obviously and particles getting spheroid after solid-solution and the amounts of spherical particles getting more and more after aging treatment.These proved that the solid-solution and aging treatment can improve the structure of Mg-Sn alloys efficiently.It can make the conclusion that the ductility and toughness were highly improved through solid-solution and aging treatment can highly improved the comprehensive mechanical properties of Mg-Sn alloys.