Study On Forging Deformation And Heat Treatment Process Of GW83 Magnesium Alloy

The GW83 magnesium alloy in Mg-Gd-Y alloy has good creep resistance and high temperature mechanical properties.But its application is restricted due to lower poor plasticity.Therefore,it is necessary to study the the strength and toughness of GW83 magnesium alloy is of great significance for the further application.In this paper,GW83 magnesium alloy was used as the research object.The effects of deformation process and heat treatment parameters on the microstructure and properties of the alloy were studied by designing the forging deformation and heat treatment experimental scheme.The article comprehensively applied a variety of material analysis methods,including microstructure observation,tensile performance test,fracture scanning and XRD diffraction analysis,systematically studied the evolution of the microstructure of GW83 magnesium alloy,and obtained the best deformation process and heat treatment process parameters.Research indicates:?1?Compared with uniaxial compression,during the multi-direction forging deformation process,coarse grainsare is broken into small ones and recrystallization is nucleated in the vicinity of the interlaced deformation zone,which make the deformed microstructure more uniform.The effect of grain refining was most remarkable after three-pass multi-direction and the average grain size is 14?m.Meanwhile the alloy has obtained the most excellent mechanical properties.The tensile strength,yield strength and elongation are respectively 321MPa,253 MPa and 10.6%.The fracture morphology shows a large number of dimples as a typical intergranular ductile fracture characteristic.?2?The GW83 magnesium alloy was heat treated after forging deformation,and the heat treatment parameters was optimized by Box-Behnken response surface method.Through the statistical analysis of the experimental results,the second-order response surface mathematical model between tensile strength,yield strength,elongation and solution temperature,solution time,aging temperature and aging time is obtained.Furthermore,the optimal parameter of the heat treatment was obtained:the solution temperature is 445?,the solution time is 10 h,the aging temperature is 224?,and the aging time is 14 h.?3?After the deformed GW83 magnesium alloy solution treated by T4?445?×10h?,the Mg₂₄?Gd,Y?₅ eutectic phase at the grain boundary is basically dissolved,and the Gd and Y elements are fully dissolved into the matrix to form a supersaturated solid solution.At the same time,a small amount of Mg₅?Gd,Y?phase is precipitated.After heat treatment at T6?445?×10h+224×14h?,a large number of uniformly distributed metastable?'-Mg_3?5RE strengthening phase precipitated,which effectively improved the mechanical properties of the alloy.According to the fracture analysis of GW83 magnesium alloy under different heat treatment conditions,after T4?445?×10h?solution treatment,there are a large number of dimples in the fracture,which is ductile fracture..After T6?445?×10h+224×14h?treatment,there are a large number of small and shallow dimples and a small number of cleavage planes in the fracture,which shows a composite fracture mode in which toughness and brittle fracture coexist.?4?Comparing the test results,the as-cast GW83 magnesium alloy is heat-treated by T6?445?×10h+224×14h?after three-passes multi-direction forging deformation,and the toughness and yield strength of the alloy are greatly improved.The mechanical properties is increased from the original 210 MPa,167 MPa,2.8%to 354.6 MPa,268.3 MPa,and 12.05%.