Effect Of Y And Ni On Microstructure And Properties Of Cu-Cr Alloy

Cu-Cr alloys are widely used in aerospace,lead frames,and high-speed rail contact lines because of their high strength and good electrical conductivity.Regulating the precipitation and growth behavior of the second phase in Cu-Cr alloys by microalloying with a suitable deformation heat treatment process is one of the main ways to further improve the strength,electrical conductivity,and softening resistance of Cu-Cr alloys.The properties of Cu-Cr alloys are closely related to the second phase in the precipitation morphology,structure and the growth behavior during aging.The influence of different elements on the properties of Cu-Cr alloys is also mainly reflected in the different roles of alloying elements on the nucleation and growth of the second phase and its structural evolution.In this paper,Cu-Cr,Cu-Cr-Y and Cu-Cr-Ni alloy ingots were prepared in a vacuum melting furnace.After the alloy was subjected to solid solution-aging,the effects of adding Y and Ni alone on the structure and properties of Cu-Cr alloy were studied,and the effects of Y and Ni on the precipitation behavior of the precipitated phases were investigated.The alloy plates were made by the process of "hot rollingsolid solution-cold rolling-aging" process,and the effects of Y and Ni on the organization,strength,and softening resistance of Cu-Cr alloys under different deformation and heat treatment processes were studied.The Cu-Cr-Y and Cu-Cr-Ni alloys’ s structure-effect relationship between the ways of process,structure and property was clarified.The main results of the study are as follows:The addition of trace Y elements can refine the as-cast Cu-Cr alloy structure.When Cu-Cr-Y alloy is aged at 450 ℃,the peak hardness reaches 130.6 HV0.5,the conductivity is 90.2 %IACS,and the nano Cr precipitated phase has fcc structure.The peak hardness of Cu-Cr-Y alloy reached 164.5 HV0.5 after 90% cold rolling and was aged at 450 ℃,which was 24.1 HV0.5 higher than that of Cu-Cr alloy,and the conductivity remained above 90 %IACS.The addition of Y retards the recovery and recrystallization of the Cu-Cr alloy after cold deformation aging so that the Cu-Cr-Y alloy retains a large amount of substructure and a small amount of deformation during peak aging with little effect on the electrical conductivity.Strength theory calculations reveal that dislocation strengthening and precipitation strengthening are the main reasons for the higher strength of Cu-Cr-Y at this time.The hardness,electrical conductivity,and softening temperature of Cu-Cr-Y alloy increased with the increase of deformation,and the softening temperature was as high as 570 ℃ when the cold rolling deformation was 90%.When the Cu-Cr-Ni alloy was aged at 450 ℃,the peak hardness was 124.6 HV0.5,the conductivity was 83.2 %IACS.The nano-Cr precipitation phase of the peak-aged Cu-Cr-Ni alloy has a bcc structure.The precipitation sequence of the second phase of the solid-solution Cu-Cr-Ni alloy during holding and aging at 450 °C is the supersaturated solid solution-fcc-Cr phase-bcc-Cr phase.The Cu-Cr-Ni alloy was deformed by 90% cold rolling and held for aging at 450 ℃,at which time the peak hardness reached 144.5 HV0.5 and the electrical conductivity was 89.3 %IACS,and the alloy still maintained high electrical conductivity,at which time the nano-Cr precipitated phase was fcc structure.The softening temperature of the Cu-Cr-Ni alloy with 90% cold rolling deformation is 470 °C.