Effects of Extrusion Height on Microstructure and Properties of 7075/6061 Composite Ingot
7075/6061 bimetal composite ingot with semi-solid structure/dendrite structure was prepared by squeeze composite casting process.The effects of of different extrusion outlet height of 7075 aluminum alloy semi-solid billet on the interfacial microstructure and hardness of composite ingot was studied.The results show that,with the decrease of extrusion height,the instantaneous bonding temperature of the interface increases,which leads to a significant increase in the width of the composite interface.The microstructure at the interface is fine,and there is convection diffusion behavior of alloy elements,which makes the hardness of the composite interface higher than that of the metals on both sides.However,when the extrusion height is smaller,the thermal effect on the interface structure is severe and the grain coarsening is serious,resulting in the overall decrease of the interface strength.Therefore,when the extrusion height is 250 mm,the microstructure of the composite ingot interface is better,which is fine equiaxed grains and α-Al solid particles are evenly distributed,the interface hardness is higher and the transition is smooth.
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