Study On Microstructure And Properties Of Cu-Cr-Zr Alloy

Due to excellent electrical and thermal conductivity,high softening temperature,and good wear resistance,Cu-Cr-Zr alloys have been widely used in lead frames,crystallizer linings,resistance welding electrodes and aerospace industries.At present,methods of alloying and thermomechanical treatment are adopted to improve the electrical and mechanical properties of the Cu-Cr-Zr alloys.In present investigation,microstructures,mechanical properties and electrical properties of Cu-Cr-Zr alloys respectively treated by solution treatment+aging,solution treatment+cold rolling+aging and solution treatment+aging+cold rolling+annealing were studied by means of microstructural analysis(OM,SEM,and EBSD)and microhardness and conductivity tests.In addition,based on the variation of electrical conductivity in the aging process of the alloys,the phase transformation kinetics of the alloys was studied.The main conclusions are as follows:(1)The solution-treated Cu-Cr-Zr alloys were aged at different temperatures.During the aging process,the microhardness increased rapidly as the aging time increased,and then decreased gradually after reaching the peak value.The electrical conductivity increased rapidly at the early stage of aging,and varied little as the aging time increased.For the Cu-Cr-Zr alloys aged at 460? for 8h,the electrical conductivity was 71%IACS and the microhardness was 150.71HV.(2)For the Cu-Cr-Zr alloys treated by solution treatment+cold rolling+aging,during the aging process,microhardness increased rapidly as the aging time increased,and then reached a plateau after peak value.As the aging temperature increased,the microhardness decreased.The electrical conductivity increased rapidly at the early stage of aging,and varied little with the extension of the aging time.In addition,the cold rolling reduction had little effect on the electrical conductivity.For Cu-Cr-Zr alloys with 80%cold rolling reduction aged at 460? for 3h,the microhardness was 173HV and the electrical conductivity was 70.6%IACS.(3)For the Cu-Cr-Zr alloys treated by solution treatment+aging+cold rolling+annealing,the microhardness was about 170HV and the electrical conductivity was about 60%IACS after aging at 460? for 1h.In the subsequent annealing process,the microhardness varied little at the early stage and then decreased rapidly as the annealing temperature increased.The electrical conductivity increased firstly and then decreased as the annealing temperature increased.For the Cu-Cr-Zr alloy with 80%cold rolling reduction annealed at 500? for 3h,the microhardness was 182.4HV and the electrical conductivity was 73%IACS.(4)Based on the changes of the electrical conductivity of Cu-Cr-Zr alloy during aging,the Avrami phase transformation kinetics equations were used to describe the aging process of Cu-Cr-Zr alloy and electrical conductivity equations of Cu-Cr-Zr alloy were obtained.