Study On Hot Isostatic Pressing Processing Of ZLSi7Cu2Mg Alloy

ZLSi7Cu2Mg alloy becomes one of the widely used alloys for industrial applications forit has not only good casting properties but also a good air seal property. Vehicle engine blocks,cylinder heads and other aluminum castings with complex shape or withstanding great loads,so the high mechanical properties of them are required. Eliminating internal casting shrinkage,shrinkage porosity and other inner casting defects is one of the important way to improvecasting density and mechanical properties required in application.In this paper, hot isostaticpressing (HIP) technique is applied to achieve this goal, and then we study the HIP processingof ZLSi7Cu2Mg alloy.In this thesis, ZLSi7Cu2Mg alloy as the research object. First of all, the deformationbehaviors for ZLSi7Cu2Mg alloy at high temperatures have been investigated, and make fourrational HIP technology programs. Further, preparing for the original(non-HIP) and HIP-ed(four technology programs) alloy castings, the analysis methods of metallography,tensile testand fractography were used to compare the performance of the microstructure andsummarizes the changes of their microstructure and performances after HIP process. Finally,the mechanical properties of those HIP-ed castings at different technology programs arecompared, and then we develop the best HIP technology program of ZLSi7Cu2Mg alloy.The results had been obtained as follows:The flow stress at high temperature of ZLSi7Cu2Mg alloy is related to temperature,strain rate and deformation, accordingly reducing with the increasing in temperature and thedecreasing of strain rate.ZLSi7Cu2Mg alloy castings after HIP process can effectively eliminate themicroporosity and pinhole defects, especially for thin-walled or smaller size castings.Some pores in the castings have been compacted or pressured in some degree, but there arefew pores difficult to eliminate. The microstructure of ZLSi7Cu2Mg alloy do not significantly be changed after HIP process.The mechanical properties of ZLSi7Cu2Mg alloy after HIP process have been improvedin some degree, especially in elongation,and the tensile strength just be improved slightly.The fracture surface of tensile test specimens,all showing typical ductile fracturecharacteristics,are not being changed.For ZLSi7Cu2Mg alloy,within a certain range of HIP process parameters, the greaterpressure or the higher temperature, the more conducive to enhance the mechanical properties.In addition, for the main processing parameters of HIP such as temperature and pressure,thetemperature is more effective. Finally, this project eventually worked out the best HIPtechnology program, the temperature and pressure parameters separately is450℃,120MPa.