Study Of Microstructure And Mechanical Propetries Of AM60Alloy Containing Ce And Ca

Today energy crisis and environment pollution have become the two topics of mostconcern. A practical method can solve that two problems is to reduce the weight of vehicles.Magnesium alloy is an ideal material in automobile industry for weight reduction thanks tothese advantages such as low density, high specific stiffness, high specific strength and goodmechanical process property and so on. However, a major of magnesium alloys have poorhigh-temperature behavior, because of this shortage the application range of magnesiumalloys is limited, so developing new heat-resistant magnesium alloy is a meaningful research.In this experiment we put Mg-Ce and Mg-Ca intermediate alloys into molten AM60alloy after stirring5minutes pour into the metal mold, then we get the alloys as designed andtake some of these alloys to do T4or T6heat treating. In order to find out the mechanicalproperties of those alloys in as-cast state, as-T4state and as-T6state we carry out roomtemperature tensile test, microhardness test, macrohardness test and high-temperature creeptest. Researching microstructure evolution of those alloys by using OM, SEM, EDS andXRD.The study found out there are a great number of dendrites in as-cast AM60magnesiumalloy and the grain size of these dendrites is very large. Such microstructure can be improvedby adding Ce alloying element, the number and grain size of dendrites decrease sharplyfurther more some acicular crystals appear in the grain boundary and restrain β-Mg17Al12generate somehow. On that basis add different count of Ca （0.5wt.%².5wt.%） alloyingelement the grain size decrease further. The number of β-Mg17Al12gradually decline with Cacontent increasing, on the contrary Al₂Ca accumulate more and more and shape herringbone texture nearby the grain boundary finally. All the dendrites of AM60Ce1Ca3alloy haveturned to equiaxial crystal. There are few β-Mg17Al12can be found and Al₂Ca become themain strengthening phase. When the count of Ca in the alloy beyond1.341wt.%, Al₂Cabecome larger and connect into net structure.The study of mechanical properties shows that thanks to fine-grain strengthening thetensile strength, elongation rate, hardness and high-temperature creep resistance of as-castAM60Ce1alloy have varying degrees of improvement. After adding different count of Ca（0.5wt.%².5wt.%） into AM60Ce1alloy, mechanical properties have changed in differentways. As the count of Ca increase tensile strength and elongation rate behave enhance in thebeginning and get maximum value at AM60Ce1Ca3alloy and then descend in the end.However, hardness and high-temperature creep resistance strengthen with the count of Caincrease. Considering these mechanical properties and microstructure of alloys we regardAM60Ce1Ca3alloy as the best alloy in this experiment.Comparing the microstructure and mechanical properties of the alloys in as-cast state,as-T4state and as-T6state we can know that β-Mg17Al12is much more sensitive than Al₂Cato the heat-treating. Observing AM60alloy, AM60Ce1alloy and the alloys with few count ofCa we can find that most of β-Mg17Al12dissolved in the matrix so that their matrix becomesmoother and grain boundary become clearer after solid solution treatment. Then after aging20hours β-Mg17Al12separate out near the grain boundary again and the grain size growlarger at the same time. No matter in which state AM60Ce1Ca3alloy has bigger tensilestrength than other alloys. Its’ tensile strength and Brinell hardness behave best in as-T6statebut its’ microhardness and high-temperature creep resistance behave best in as-T4state.