Effect Of Rare Earth Elements Y And Nd Addition On Microstructure And Properties Of Mg-Al-Ca Alloy

Mg-Al-Ca alloys have high mechanical properties at high temperature,good corrosion resistance and other excellent features,with great potential and prospects for development in the aerospace,automotive,electronic information products in the field.However,Mg-Al-Ca alloys have poor castability in the casting process,more prone to deficiencies that limit its widespread use.In this paper,Mg-Al-Ca-based alloy by adding small amounts of rare earth elements to improve the defects of the alloy during casting,in order to obtain high temperature properties of magnesium alloy having a low cost.In this paper,a metal mold casting method with Mg-5Al-5Ca alloy as the matrix,by adding different amounts of the individual rare earth elements Y,Nd and rare earth elements added separately mixing varying amounts of added varying amounts of Y and Nd,respectively,to prepare an Mg-5Al-5Ca-x Y（x=0,0.5,1,1.5）alloy,Mg-5Al-5Ca-y Nd（y=0,0.5,1,1.5）alloys and Mg-5Al-5Ca-x Y-y Nd（x=0,0.5,1,1.5 y=0,0.5,1,1.5）alloy.Scanning electron microscopy（SEM）,energy dispersive spectroscopy（EDS）analysis and the like morphology microstructure by means of analysis by optical microscope（OM）,X-ray diffraction（XRD）,determined with the addition of rare earth elements,magnesium the composition of each phase is generated in the alloy structure,the number,size and distribution.By Vickers hardness tester,the electronic testing machine universal mechanical testing means of adding different rare earth element magnesium alloy content and high temperature is room temperature（150oC,175oC）mechanical properties in the state of the test,with magnesium alloys with different contents of rare earth changes of mechanical properties of the elements added.The results showed that the addition of rare earth elements Y different content in Mg-5Al-5Ca-x Y（x=0,0.5,1,1.5）alloy,was found Mg-5Al-5Ca alloy by a rare earth element is not addedα-Mg matrix phase and a skeletal phase coarse Al₂Ca,Mg₂Ca phase.With the addition of Y,resulting in a bright white Al₂Y new rare-phase phase,uniformly distributed in the alloy matrix and the grain boundaries,and refine the microstructure of the alloy and more uniform distribution.When the addition of Y in an amount of 1%Y,the most obvious effect of refining the alloy structure,at this time Mg-5Al-5Ca-1Y alloy has optimum mechanical properties at room and high temperature tensile strength is 125MPa（room temperature）,96.31MPa（150oC）,94.90MPa（175oC）,3.0%elongation（room temperature）,4.6%（150oC）,5.8%（175oC）,hardness value 93HV,respectively.Different content of Nd is added to a Mg-5Al-5Ca-y Nd（y=0,0.5,1,1.5）alloy,the alloy phase consists ofα-Mg matrix phase,phase skeletal Al₂Ca,Mg₂Ca and bright white the new rare-earth phase Al₂Nd phase,no other phase formation.With the increase of Nd content,the degree of refining alloy is increasing,a new generation of rare-earth phase is uniformly distributed in the alloy matrix and the grain boundaries,when the content of Nd is added 1%Nd alloy Refinement the most obvious effect,when the content of rare earth is added excessively,coarse alloy tends phenomenon,at this time Mg-5Al-5Ca-1Nd optimum mechanical properties of the alloy,the maximum values of tensile strength 124.9MPa（room temperature）,112.2MPa（150oC）,99.87MPa（175oC）,the maximum elongation value of 2.9%（room temperature）,4.4%（150oC）,5.4%（175oC）,the maximum hardness of 94HV,respectively.Mix was added varying amounts of Y and Nd to Mg-5Al-5Ca-x Y-y Nd（x=0,0.5,1,1.5,y=0,0.5,1,1.5）alloy,not only by the alloy at this timeα-Mg and Al₂Ca,Mg₂Ca phase,also produced a new phase of rare earth Al₂Y,Al₂Nd phase,uniformly distributed in the alloy matrix and the grain boundary,consumes a large amount of alloy elements Al,strongly suppressed the coarse Mg matrix and a skeletal phase and Al₂Ca,Mg₂Ca is generated,a good improved morphology alloy,refining alloy.When the mixing amount of the rare earth is added 1%Y+1.5%Nd alloy during refining effect is most obvious,the best case,the maximum tensile strength of Mg-5Al-5Ca-1Y-1.5Nd mechanical properties of the alloys is 157 MPa（room temperature）,153MPa（150oC）,121.8MPa（175oC）,a maximum of 4.6%elongation（room temperature）,5.8%（150oC）,7.6%（175oC）,the maximum hardness of 99HV,respectively.Comparative analysis of the study results of the foregoing Mg-5Al-5Ca-1Y-1.5Nd alloys have optimum mechanical properties,the alloy processing different heat treatment process,found that the solution temperature of the alloy at 420℃,solution time of 24h,the aging temperature is 200oC,aging time of the heat treatment process for 12h,the effect of improving the alloy most obvious,reaches the maximum mechanical properties,tensile strength value162.30MPa（room temperature）,155.60MPa（150oC）,125.40MPa（175oC）,5.0%elongation（room temperature）,6.2%（150oC）,8.0%（175oC）,the hardness value of 100HV.