Effect of T6 Heat Treatment on Microstructure and Properties of Ti@(Al-Si-Ti)p/A356Al Composites Fabricated via Powder Thixoforming
An A356 Al alloy based composite reinforced by core-shell structured(CS)particulates was prepared by powder thixoforming,and then the comprehensive mechanical properties of the composite were further improved by T6 heat treatment.The results show that the CS particulates not only improve the ultimate tensile strength and yield strength of the composite(increased by 18.0％and 32.7％,respectively),but also render the composite an excellent elongation of 10.8％equivalent to that of the A356 alloy(12.4％).During the T6 heat treatment,the strength and hardness of the composite increase firstly(1-7 h,i.e.,under-aging)and then decrease(9-12 h,i.e.,over-aging)with the extension of the aging time,reaching the maximum value at 8 h(i.e.,peak aging).The ultimate tensile strength,yield strength and hardness of the composite at peak aging are 325.4 MPa,254.4 MPa and 1019.2 MPa,respectively,which are 33.7％,74.0％and 48.5％higher than those without the heat treatment,and the elongation is 9.4％,which has almost no decrease compared with that without heat treatment.In other words,after the T6 heat treatment,the CS particulates can improve the strength of the composite while retaining its good plasticity.Finally,the strengthening mechanisms of the composite were discussed by analyzing the size,density and type of the precipitates in the matrix of the composites aged for 8 and 12 h.
Al matrix compositepowder-thixoforming"core-shell"structureT6 heat treatmentmicrostructure and properties
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