Effect Of Al Content On Solidification Process And Stability Of Mg-Al-Ca-Sm Alloy

Mg-Al heat-resistant magnesium alloy is the most performance and costeffective alloy for automobile power system.However,its high temperature mechanical properties limit its extensive use in industry.The alloying of alkaline earth element Ca and rare earth element rare Sm can paly a role of flame retardant,composite alloying,metamorphism,alloy strengthening and melt purificication,so that the comprehensive properties of Mg-Al-based magnesium can be significantly improved.In this paper,a new type of Mg-Al-Ca-Sm heatresistant magnesium alloy was developed by adding the Ca and Sm to research the effect Al content on the solidification process and stability of Mg-Al magnesium.In this paper,we studied the effect of Al content on the microstructure,mechanical properties,solidification process and stability of Mg-Al-Ca-Sm magnesium by the means of XRD,OM,SEM,EDS,TEM,hardness test,tensile properties test,solidification curve test,remelting-water quenching test,isothermal treatment experiment and so on.1.The results shows that: with the increasement of Al content from 3 % to 12 %,the grain size increases from 32.14 ?m to 41.05 ?m,the(Mg,Al)2Ca phase and Al11Sm3 phase disappear,and a new intermetallic phase ?-Mg17Al12 phase is formed.With the increasement of Al content,the alloy with the maximum tensile strength is 149.7 MPa when the Al content is 9 %.2.The solidification sequence of Mg-Al-Ca-Sm alloy is substantially the same.The order of the second phase sequence is ?-Mg solid solution,Al2 Sm phase,Al11Sm3 phase,Al2 Ca phase and ?-Mg17Al12 phase.The only difference is that only the Al content is 3 %,Al11Sm3 phase and(Mg,Al)2Ca phase are formed.And ?-Mg17Al12 phase is only carried out under the condition of Al content higher than 6 %.3.The Al2 Sm phase,Al2 Ca phase and Al11Sm3 phase in Mg-Al-Ca-Sm alloy are stable phase at 200 ?.However,during the isothermal treatment at 450 ?,the ?-Mg17Al12 phase phase dissolve into ?-Mg matrix,Al11Sm3 phase and(Mg,Al)2Ca phase change into another phase,while Al2 Sm phase and Al2 Ca phase are high temperature stable phases.