Study On Microstructure And Mechanical Properties Of AZ80 Composites Reinforced By La₂O₃ Nanoparticle

As the lightest metal structural material,magnesium alloy is an important choice of lightweight materials in the fields of aerospace,transportation and consumer electronics.However,due to its low strength and stiffness,magnesium alloy is often difficult to be used as the main bearing parts,which greatly limits its application field.Particle reinforced magnesium-based composite can significantly improve the mechanical properties of magnesium materials through the design of the reinforcement,but there are some problems,such as the difficulty in infiltration and uniform dispersion of the powder,the difficulty in casting and preparation,and the high cost of the reinforcement materials,which limit its application and promotion in the civil field.In order to solve the above problems,nano-oxide precursor was prepared by molten salt infiltration method.On this basis,La2O3 nanoparticle reinforced AZ80 magnesium-based composite was prepared by casting method.The effect of La2O3 addition,extrusion and heat treatment on the microstructure and mechanical properties of AZ80 magnesium-based composite was studied,and its mechanism was preliminarily analyzed.A precursor with a content of 20wt.%nano La2O3 was successfully prepared by using second flux to infiltrate the nano powder of the reinforcement,and by using the precursor,AZ80 magnesium-based composite with a content of 0.5wt.%?0.9wt.%of La2O3 in uniform dispersion was successfully prepared by the casting method.The observation of extrusion microstructure of AZ80 magnesium-based composite showed that 0.5wt.%La2O3 could refine the extrusion microstructure and improve the microstructure uniformity,so that the hardness,tensile strength and yield strength of the extruded bar could be improved,no matter the low temperature extrusion(250?)or high temperature extrusion(350?).However,when the addition of La2O3 was increased to 0.7wt.%,the non-uniform recrystallization of matrix produced by the reinforcement agglomeration resulted in the coarsening of local grains,and the hardness and strength were reduced,and this trend was aggravated with the increase of the addition of La2O3.High temperature extrusion could improve the non-uniformity of extrusion structure,but the hardness and strength of composites were reduced due to the significant coarsening of matrix grains.The hardness test results of the aging treatment of low temperature extrusion(250?)bars showed that,within the conditions of this study,there were some changes in aged hardness,but none were significant.AZ80 and AZ80-0.9La2O3 were aging hardening,AZ80-0.5La2O3 was aging softening,and AZ80-0.7La2O3 had no significant changes.The tensile test showed that low temperature(150?)heat treatment of AZ80 and AZ80-0.5La2O3 did not significantly change the tensile strength,but reduced the elongation.High temperature aging had a softening effect.