Effect Of Trace Element Mn/Sc On Mg-8Zn-0.5Cu Alloy

Magnesium alloy has a relatively perfect advantages of die casting technology,with the emergence of mobile phone/5 G base station application demand,high strength and formability of magnesium alloy and high thermal conductivity has a higher request,while adding rare earth in magnesium alloy can obviously improve the high temperature strength and casting performance of alloy,on the other hand also increases the production cost of magnesium alloy and alloy weight,Further research and exploration of new high performance magnesium alloys are needed.In order to ensure the strength and reduce the cost,this paper added trace elements on the basis of Mg-8Zn-0.5Cu ternary alloy,and explored the influence of trace elements and deformation process on the microstructure and mechanical properties of the alloy before and after heat treatment.This paper aims at the different characteristics of different strengthening factors in the Mg-8Zn-0.5Cu system,some experiments add Mn element to form the elemental phase of Mg-Mn,and regulate the morphology and distribution of the elements.In the other part of the experiment,Sc element was added to form Sc₃Zn₁₇ reinforcer.The shape and distribution of the second phase were regulated by the content of Sc to improve and promote the aging effect of Zn.The as-cast Mg-8Zn-0.5Cu alloy is composed ofα-Mg+Mg Zn₂+Mg Zn Cu phase,and the second phase is mainly distributed in a network along the grain boundary,in which the content of Mg Zn₂ is more and the content of Mg Zn Cu is less.With the addition of Mn element,the grain size of the alloy is refined,which hinders the growth of the second phase.With the addition of Mn element,the mechanical properties of the alloy show a trend of increasing first and then decreasing.Mg-8Zn-0.5Cu-0.5Mn alloy has the best mechanical properties,and its yield strength,tensile strength and elongation can reach 103MPa,227MPa and 6.8%.After 360℃rolling deformation of Mg-8Zn-0.5Cu-x Mn alloy,Mn elemental phases and Mg Zn₂ phases are rolled into fine rods and points along the rolling direction,which is beneficial to hinder the growth of dynamic recrystallization grains and play the role of refining grains.The Mg-8Zn-0.5Cu-0.5Mn alloy has the best properties after rolling,with the tensile strength of 268MPa,elongation of 21%and yield strength of 147MPa.The as-cast Mg-8Zn-0.5Cu alloy is composed ofα-Mg+Mg Zn₂+Mg Zn Cu phase,in which the content of Mg Zn₂ is more and the content of Mg Zn Cu is less.With the addition of Sc element and the introduction of the new second phase of Sc₃Zn₁₇,the content of Mg Zn₂decreased,and the microstructure of the alloy showed obvious dendritic growth to all sides,and the dendritic arms（SDAS）decreased gradually.With the addition of Sc element,the mechanical properties of the alloy firstly increase and then decrease.Mg-8Zn-0.5Cu-0.5Sc alloy has the best mechanical properties,and its yield strength,tensile strength and elongation can reach 185MPa,294MPa and 10.2%.