Study On Preparation And Properties Of AZ91 Foam Magnesium Alloy

Magnesium and magnesium alloys are widely used in automobiles,aerospace,medical,military,3C and other industries.due to their excellent properties such as light weight,high specific strength,high specific stiffness,good biocompatibility,and excellent electromagnetic shielding properties^[1].The pore-forming agent is added on the basis of the magnesium alloy.The foamed magnesium alloy prepared by the powder metallurgy method also has excellent properties such as light weight,energy absorption,sound absorption,heat dissipation,biocompatibility,and shock resistance^[2].So that it has a wide range of applications.In order to further study and optimize the effects of the preparation process of foamed magnesium alloy,the amount of urea added,and the alloying element Sn on the structure and properties of the foamed magnesium alloy,a powdered metallurgical method was used to prepare the foamed magnesium alloy.And using the anti-compressive performance test,XRD phase analysis,micro-hardness test,Image J,metallographic test,corrosion resistance test and other means to discuss the effect of process parameters,pore-forming agent content,and addition amount of Sn powder on the microstructure and properties of foamed magnesium alloy.Then drawing the following conclusions:1 11MPa is the best pressing pressure.At this time,the pore distribution of the material is relatively uniform,and the thickness of the pore wall is relatively thick,so that the sample is not prone to failure;the appropriate pressing pressure increases the density of the material,increases the plastic bonding between the materials,and facilitates the generation of the sintering neck.2 520℃is the optimum sintering temperature process parameter.At this time,the pore distribution of the material is uniform and the size matches the pore size of the bone,and the mechanical properties are optimized.3 1.5 hours is the optimum holding time process parameter.At this time,the pore morphology and mechanical properties are good,and at the same time,the stress platform is relatively stable and is closer to the ideal foam metal.4 We successfully prepared AZ91 foam magnesium alloy with a porosity of37.95%～67.58%.The shape of the pores presents a variety of shapes,mainly connected by macropores and macropores,and accompanied by macropores and micropores,and connections between micropores and micropores;60vol%is the optimal urea volume addition.At this time,the pores of the sample are in a semi-open state,and the compressive strength and Young’s modulus of the material also meet the mechanical properties of cancellous bone.The collapse platform of the stress-strain curve is relatively flat,the mechanical properties are stable,and it is suitable for biological materials.5 The addition of Sn element to the AZ91 foam magnesium alloy has a significant effect on the phase composition,mechanical properties and corrosion resistance of the material:The pore wall phase composition of foamed AZ91-XSn magnesium alloy is mainly Mg₂Sn,β-Mg₁₇Al₁₂,α-Mg.With the increase of Sn content,the characteristic peaks of Mg₂Sn andβ-Mg₁₇Al₁₂became more and more obvious,indicating that the content of Mg₂Sn andβ-Mg₁₇Al₁₂in the matrix gradually increased.Mg₂Sn can promote the formation ofβ-Mg₁₇Al₁₂,so that the pore wall is more tightly combined,and the thickness of the pore wall of the material is reduced.The sintering neck tends to be smooth,the pore size becomes larger,the atomic diffusion is intensified,and overburning occurs.A large amount of liquid phase causes the shrinkage of pores to increase,and the pore size decreases later.The addition of Sn element can improve the mechanical properties of the material.When the amount of Sn element added is 1.0wt%,the compressive strength and yield strength reach the maximum,which are:11.83MPa and 9.46MPa,respectively.The composition process of Sn in the matrix is cold,resulting in fine grains and fine grain strengthening;Mg₂Sn hinders grain boundary slip and crack diffusion.Improved mechanical properties.In the later period,the coarse grains and the decomposition of urea destroy the sintering neck,which reduces the mechanical properties.Sn element can improve the Vickers hardness value of the material.Sn element can achieve fine crystal strengthening,make the material dense and improve the hardness.Sn element can reduce the sliding friction factor of AZ91 foam magnesium alloy.Sn element can improve the corrosion resistance of the material.When the added amount is 1.5wt%,the material has the best corrosion resistance.The addition of Sn element makes the matrix fine grain strengthening and increases the corrosion potential of the magnesium alloy matrix.When it exceeds 1.5wt%,the content of Sn element is excessive,and the presence of a large amount of Mg₂Sn andβ-Mg₁₇Al₁₂will provide a greater driving force for galvanic corrosion.At the same time,the aggregation of fine grains makes the grains coarse,resulting in a reduction in corrosion resistance.