Microstructure And Mechanical Properties Of Die-casting AZ91-Ce Magnesium Alloy

Magnesium alloys are widely used in aerospace,automotive and other industries due to their advantages such as low density,high strength,and excellent heat resistance.Research on improving the comprehensive performance of magnesium alloys has also been increasingly deepened.The performance of magnesium alloy is usually improved by improving alloy composition,optimizing casting and heat treatment processes,among which the improvement effect of microalloying is more significant.At present,the research on the influence and laws of Ce on die-cast magnesium alloy is not perfect.This article mainly studies the effect of adding rare earth element Ce on the microstructure and mechanical properties of as-cast AZ91 magnesium alloy,and selects the optimal die-casting process parameters to test and analyze the alloy die-casting performance.First,gravity casting experiments were conducted to analyze the effect of Ce addition on the mechanical properties and structure of AZ91-xCe alloy.The addition of a small amount of Ce generates a high-melting thermally stable phase Al4Ce,and the alloy porosity also decreases.The experimental results show that the fine grain,precipitated phase and solid solution strengthening are strengthened together,and the tensile strength and yield strength of AZ91-xCe alloy have been significantly improved.By comparing and observing the mechanical properties and organization of alloys with different Ce content,it is concluded that when the Ce content is 0.5%,the comprehensive performance of the alloy reaches the best.Compared with AZ91 alloy,the tensile strength is increased by 29%,the yield strength is increased by 34%,and the elongation is also slightly increased.Using ProCAST simulation software,the thermodynamic coupling model of the best Ce content AZ91-0.5Ce magnesium alloy was established to calculate the alloy physical parameters and other parameters related to the alloy performance,on the basis of which the filling and solidification process of the alloy was simulated and calculated.Analyze and compare the distribution of alloy temperature field and shrinkage shrinkage cavity under different process parameters to optimize the selection of the best die casting process parameters.Based on the simulation results,the production parameters are adjusted.When the pouring temperature is 675?,the mold preheating temperature is 200?,and the pouring speed is 1.5m/s,the alloy performance is the best.With reference to the numerical simulation results,different process parameters were used to produce die-cast magnesium alloy castings,and the tensile properties and micro-morphology of the alloy were studied and analyzed.Compared with the gravity casting method,the "?-Mg"primary phase of the alloy sample produced by pressure casting is finer and has better tensile and yield strength.The experimental results show that when the casting temperature is 675?,the mold preheating temperature is 200?,and the casting speed is 1.5m/s,the casting has the best comprehensive performance.The tensile strength,yield strength and elongation can reach 280MPa,250MPa and 1.98%respectively.Observation of changes in casting mechanical properties and microstructures caused by differences in process parameters,it is concluded that pouring temperature has the greatest effect on mechanical properties and mold preheating temperature has the smallest effect,which is basically consistent with the simulation results.