Studies On The Effect Of Cr Content On Microstructure And Properties Of Cu-Cr-Zr Alloy

The thesis takes three Cu-Cr-Zr alloys with different Cr contents as researchobjective and conducts casting, forging, extrusion and solution aging treatment of thealloys.By means of using the optical microscope, scanning electron microscope,microhardness tester, tensile experiment and other testing measures, this paper analyzesthe influence of Cr content on the structure and performance of the Cu-Cr-Zr alloys.The research findings are as follows.Three Cu-Cr-Zr alloys are prepared by vacuum mid-frequency inductionfurnace.The contents of compoundly-added Cr are (WCr=0.69%、0.86%、1.0%). Thealloy as-cast organization analysis has indicated that the higher the Cr content is, themore serious the crystal boundary segregation of the Cu-Cr-Zr alloy is. Themicrohardness and tensile strength of the alloy increase as the Cr content gets higher,while the ductility and electric conductivity of the Cu-Cr-Zr alloys witness a declinewhen the content increases. The segregation of Cr has been improved and itsdistribution is more uniform after Cu-Cr-Zr alloy goes through as-cast alloyhomogenization treatment.After hot-work(forging and extrusion) of Cu-Cr-Zr alloys with different Crcontents, it is inferrable from organization and performance analysis that hot-work canbread down bulky crystals in alloy and greatly reduce crystal size, which isapproximately10μm after extrusion.The tensile strength of the alloys in the forgingstate increases with the increase of Cr content while the conductivity of the alloysdeclines with the increase of Cr content. Aging treatment directly after the solution treatment is adopted by this experimentas the heat treatment process. By analyzing the change of the hardness and conductivityof the alloys, the best heat treatment process is come up with, i.e. solid solution980℃insulation40min+water quenching+460℃3h+air cooling.An analysis is performed regarding the structure and performance of the alloyswith different Cr contents after different heat treatment processes. For the Cu-Cr-Zralloys which go through solution and aging treatment, the higher the Cr content is, themore the precipitated phase is. The microhardness and tensile strength of the alloys seea maximum when the content of Cr is0.86%.σ0.86Cr铸=330.8MPa、σ0.86Cr锻=404.5MPa、σ0.86Cr挤=431.7MPa、HV0.86Cr铸=142.9Hv、HV0.86Cr锻=138.9Hv、 HV0.86Cr挤=135.5Hv。...