Effect Of Ce And Sn On Microstructure, Mechanical Properties And Corrosion Resistance Of AZ80Magnesium Alloy

AZ80magnesium alloy is one of most commomly used alloys of the typical AZ-series magnesium alloys which own many characteristics such as high strength, good ductility and corrosion resistence and so on. Although It has owned so many advantages, the thick network morphology P-Mg17Al12phases that assemble in crystal grain boundary severely limited the improvement of performances of AZ80alloy no less than other AZ-series magnesium alloys, which seriously limited the its improvement in the production application. The work mainly choose the AZ80magnesium alloy as the research object.Rare earth elements as the alloying elements have been widely used in magnesium alloy components, because they can purify the magnesium alloy melt, improve the microstructure and casting performance of the alloy, inhance the strength at room and high temperature and corrosion resistance of the alloy and so on. Sn elements also has the very good effect on strengthening Mg-Al series magnesium alloy, especially improve the yield strength of the alloy. The studies have shown that micro-alloying with compound addition of Sn and Ce elements to magnesium alloy can also effectively improve the microstructure of magnesium alloy. Based on the idea that micro-alloying improve the magnesium alloy in this work, the effects of separate addition of Ce and compound addition of Ce and Sn on the microstructure, mechanical properties and corrosion resistance of AZ80magnesium alloy were studied by the additional ways. And then the strengthen research in the experimental alloy with optimal composition was studied with the way of heat treatment. By means of the analysis tools of OM, XRD, SEM and EDS and various methods of mechanical properties testing, the changing trends of microstructure, mechanical properties and corrosion resistance of experimental alloy were studied in detail. The research results are as follows:1) Organization of AZ80magnesium alloy is mainly composed of a-Mg matix, continuous network β-Mg17Al12phases and a small amount of Al8Mn5phases. With the appropriate amount addition of Ce, not only matrix organizations were refined visibly, but also β-Mg17Al12phases were modified well with the continuous network turning to small island-like distribution even to granular along grain boundary. The new generations of acicular A14Ce phases were evenly distributed in the grain and along grain boundary. When adding the appropriate amount of Sn to the alloy, matrix organizations and β-Mg17Al12phase were further refined. Compared to separate addition of Ce, acicular A14Ce phases became more short and homogeneous even when alone. And the newly generated massive Mg2Sn phases were evenly distributed in the grain and along grain boundary.2) As the Ce content increased, macro hardness of the as-cast experiment alloy was linearly increased, but impact toughness, tensile strength and elongation were firstly increased and then decreased. When Ce content was1.00wt.%, the comprehensive performances of the experiment alloy were the best, such as the macro hardness, impact toughness, tensile strength and elongation were61.90HB,15.50J·cm-2,15.50MPa and3.35%. When Compound add Ce and Sn to the alloy, with the increase of Sn content, the trends of the comprehensive performances of the experiment alloy were the same as that of the experiment alloy with separate addition of Ce. When the addition amount of Sn was1.00wt.%, the mechanical performances of the as-cast experiment alloy were the best. And the values of macro hardness, impact toughness, tensile strength and elongation were61.80HB,15.00J·cm-2,194.50MPa and3.68%respectively, and increased by9.78%,57.89%,57.89%and9.78%respectively compared with AZ80magnesium alloy.3) Ce and Sn Element have a certain positive effect on enhancing the corrosion resistance of AZ80magnesium alloy.4) The heat treatment with solid solution for2h at425℃and ageing for20h at200℃were best suited for AZ80+1.0%Ce+1.0%Sn alloy. After the solution for2h at425℃, β-Mg17Al12phases in the organization are dissolved in the a-Mg matrix, yet the morphology and distribution of Al4Ce and Mg2Sn phases did not change obviously. By this way of the heat treatment, macro hardness, tensile strength and elongation of AZ80+1%Ce+1%Sn experiment alloy reached72.7HB,243.4MPa and6.47%, respectively. Compared with of the as-cast AZ80+1.0%Ce+1.0%Sn experimental alloy, the values of three performances were increased by17.6%,25.1%and75.8%respectively, which basically satisfy the mechanical performance requirements of the commercial automobile wheel material.