Effect of Heat Treatment on Microstructure and Properties of AlZn4SiPb Alloy

In this paper,AlZn4SiPb ingots were prepared by metal mould,the ingots were rolled to 2mm after homogenization heat treatment.The microstructure,hardness and strength of ingots and 2mm plates after heat treatment were tested.The results show that the segregation of Pb element is serious.The content of Pb in the ingot casted later is relatively higher.The Pb phase is distributed in grains and grain bounbaries in spherical or strip shape.Homogenization heat treatment has no obvious effect on the morphology of Pb phase.After heat treament,the hardness of alloy ingot is increased from 78.9 HV to 89.8 HV.The cold rolled sheet has fibrous structure.With the increase of heat treatment temperature,the hardness and strength of the sheet decreased first and then increased.After 300℃ heat treatment,the hardness of the sheet is 45.5 HV,the tensile strength is 179MPa.After 500℃ heat treatment,the hardness of the sheet is 90.9 HV,the tensile strength is 306 MPa,the elongation is 28.5%.