Study On Microstructure And Properties Evolution Of Mg Alloy In Heat Treatment After Forging Forming Process

Magnesium alloys have found wide variety of applications in different industries, due to its low density, high specific strength& stiffness and good damping capacity. Among the commercial magnesium alloys, AZ series wrought Mg alloys have become one of the most important wrought Mg alloys in the field of industries because of its good processing property.As a part of the"Net-shape forming via close die pressing of extruded perform"patent. The microstructure and properties of AZ61, AZ61E and AZ81 alloy in as forged and aging states were investigated with hardness test, optical microscopy, X-ray diffraction (XRD), tensile test and scanning electron microscopy (SEM) analysis. Laid the foundation of using extrusion-forging forming process to produce high toughness magnesium alloyThe main conclusions are as follows:①The obtained results indicate that during the isothermal forging, At 60% compression ratio, 400℃deformation temperature, 5.6mm/s deformation velocity isothermal forging in this study, the strength of the sample AZ81 alloy further enhanced. The tensile strength, yield strength, elongation and hardness of the specimens after extruded-forging compound deformation reach 337.6MPa, 227.9MPa, 15.83% and 74.8.②Artificial aging after isothermal forging obtained the hardness peak (HRE) 86.7, the best mechanical properties of tensile strength of 355.8MPa, the yield strength of 255.28MPa, extension rate of 10.3% at 400℃×0.5 solution +200℃×20h artificial aging condition,. analysed the mechanical properties found that tensile strength and yield strength increased firstly, then as time prolonging, the elongation is reduced, and at low temperature 150℃the smallest decrease, with the temperature elevated elongation reduced increasingly. The forged specimens, Alloy phase of theβ-Mg17Al12 precipitated in the grain and grain boundaries. The room temperature tensile fractures show tough in as-forged condition while becomes a mixed ductile-brittle fracture in as- heat treatment condition.③AZ61 magnesium alloy with RE contents after isothermal forging, the best mechanical properties of tensile strength of 304.78MPa, the yield strength of 258.73 MPa, extension rate of 9.12% at 400℃×0.5 solution +200℃×15h artificial aging condition. ④AZ61 magnesium alloy with Ce content, due to its pinning to the Al element, makes the diffusion speed of Al4Ce reduced greatly, the concentration of Al inα-Mg decreased. All those lead the hardness peek of AZ61 lag behind, mechnical properties also reduced, but the rate of elogation decline is lower than AZ61.