| Flexible copper-based alloys have excellent flexibility,conductivity and mechanical properties,they are widely used in the manufacture of various current carrying elastic elements, contact springs,switches,converters,terminal type devices in medical,aerospace maritime navigation equipment, electricity and electronic instrument industries. Cu-Si-Ni alloy were prepared by Ingot Metallurgy. Using DSC,hardness measurement,tensile test at room,electrical resistance test at room temperature,XRD,optical microscopy,and SEM,the mechanical and electric properties and the microstructure of Cu-3Si-2Ni alloy after at different treatment were studied. Them were also analysed and explained in theory. The results show that:(1) During homogenization of Cu-3Si-2Ni alloy, Microstructure has been significantly changed. The dendrite structure and coarse equilibrium Phases bewteen dendrites insuper saturation solution disappeared gradually with the increase of homogenization temperature and time,and hardness has been brought down and more uniform properties of the alloy. The diffusion kinetics of the alloy elements during the homogenizing treatment was studied and the homogenizing kinetic was studied according to Fick's First Law of diffusion. According to the results of experiment and calculation,the proper homogenizing process of Cu-3Si-2Ni alloy is at 900℃for 4h.(2) After solid solution treatment,the process harden of hot-rolled specimens disappeared. And at the same time,hardness and strength decreased obviously,the matrix softens with plasticity increasing. The strueture of the alloy after solid solution consists ofα-Cu. The solution temperature plays a more important role on the properties than the time does. The suitable solution treatment of Cu-3Si-2Ni alloy is 900℃/ 45min.(3) Cu-3Si-3Ni alloy is an aging strengthing alloy,which has been solution treatment and the properties of the alloy could be further improved for the ageing heat treatment. The precipitation strengthening and the depletion of the alloy elements in the matrix caused by the precipitation of supersaturation solid solution will improve the hardness,strength and the conductibility of the alloy simultaneously.The suitable ageing treatment is 450℃/ 2h.(4) During aging process,the conductivity of Cu-3Ni-2Si alloy is increased with the amount of precipitation of the new phase,there is a linear relationship. The process of phase transformation of alloy can be reflected by the electrical conductivity was changed during aging. It is linear relationship between the electrical conductivity and the volume fraction of the new phase. As the same time, the phase transformation kinetics experience avrami equation of alloy was obtained at 450℃that is f=1-exp(-0.5085t0.4156) and the conductivity equation isσ=7.4+0.81(1-exp(-0.5085t0.4156))aging at 450℃. (5) Thermomechanical treatment(solution-cold-drawing-aging)can increase alloy's strength greatly and hardly decrease the conductibility of the alloy. The strengthening mechanisms of the alloy mainly include solution strengthening,strain-strengthening and aging strengthening.(6) Under the experimental conditions in this paper, the optimal treatment of the alloy is 980℃/45min solution water queneh-60% cold deformation-450℃/2h ageing,it's mechanical and electrical performance can reachσb=516.94MPa,σ0.2=471.81 MPa,δ=3.91%,σ=8.1%IACS, E=87GPa, elastic strain energy=1.273GPa. |
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