Research On Forming Technology And Performance Structure Of High Strength And Heat-resistant Magnesium Alloy

Magnesium alloy is the lightest metal structural materials in the engineering application,with an excellent specific strength,higher specific modulus,good damping vibration attenuation and electromagnetic shielding performance,but there are still some shortcomings,such as absolute mechanical performance is still low,room temperature plasticity and hot forming ability is poor.Therefore,it is necessary to develop higher mechanical properties,consistency of quality being good,industrialization of magnesium alloy materials and processing technology,in order to realize the further light of weapons and equipment.This paper proposed a new type of high strength heat-resistant rare earth magnesium alloys:Mg-9Gd-3Y-1.4Zn-0.5Zr(marked as GW93ZK).Through tensile experiment,heat treatment experiment,microscopic structure analysis experiment studied the mechanical properties and microstructure analysis of casting state,extrusion state,extrusion aging states,forging and forging ageing state.The results show that the mechanical properties of casting state alloy is distributed uniformly,all composed by equiaxed a-Mg grain.The grain size is reduced from center to edge,at the same time rich in rare earth phase or rich Zr phase precipitate increasely.The hardness of extrusion state alloy is distributed uniformly,the average hardness value is 97.6HV.Not fully dynamic recrystallization occurred in extrusion process,grain size refine significantly significantly then mechanical properties improved significantly,but it shows the strain hardening phenomenon and anisotropy,extrusion direction is better than that of normal direction.The maximum tensile strength is 347 MPa,yield strength is 263 MPa,elongation is 9.0%in the extrusion direction.SEM of fracture found a large number of toughness cavity and some toughness cavity is rich in rare earth phase.The strength after foring and aging is further improved.The maximum tensile strength is 412 MPa,yield strength is 305 MPa,elongation is 8.0%in the extrusion direction.Plasticity is declined,anisotropic phenomenon still exists.Fracture mechanism of this magnesium alloy is transgranular fracture of microporous gathered.The grain of magnesium alloy after forging and aging is significantly refinement,the strength of magnesium alloy after forging and aging increases again compared with forging without aging state and extrusion state.The mechanical properties of magnesium alloy still exists anisotropic phenomenon.When the temperature of tensile experiment from room temperature increased to 300 ℃ high temperature,the flow stress of every direction reduces to some extent,but the fracture strain of every direction is increased.