Aging Changes Of Alloy Microstructure And Properties Of Cu-0.33cr-0.06zr Under Direct Current Electric Field

With the excellent electrical and thermal conductivities, Cu-Cr-Zr alloy is widely applied in the field which needs high strength and high conductivity. Which solubility and relative size, number, shape, distribution of precipitation of alloying elements are the important factors affecting on the alloy microstructure and properties. With the the increase requested of conditions of service, the traditional means is difficult to further improve the overall performance of the alloy. Currently, research on aging properties and microstructures of Cu-Cr-Zr alloy was too much. But the unified agreement about precipitates category has not been arrived. To be further explored, especially in the electric field influence on the precipitation behavior of Cu-Cr-Zr alloys.This paper researches mainly on Cu-0.33Cr-0.06Zr alloy, adopting heat treatment process of solid solution, cold deformation and aging with DC electric current. The aging changes of alloy microstructure and properties of Cu-0.33Cr-0.06Zr under direct current electric field were studied. The conductivity and microhardness of the alloy after aging was measured, and microstructure was observed. According to the relationship between electrical conductivity and precipitates amount, the phase transformation kinetics and electrical equations of the alloy after aging treatment were determined.In this paper, the alloy was obtained by solution treatment first, and then drawing of80%cold deformation. The better overall performance of the alloy aged without dc current was conductivity reached83%IACS, microhardness reached195HV aged at450℃for2h. With DC current field, the efficiency of precipitation was promoted, when aging at lower temperatures, effect is more pronounced. Ageing at400℃, with the increase of current field current density, conductivity will increase. In contrast to the conductivity of the alloy aged2h without current field is75%IACS, the conductivity of the alloy aged2h with400A·cm-2current field is84%IACS. The conductivity of the alloy aged at450℃for2h with400A·cm-2current field is85% IACS, equivalent to aged for6h without current field. When the alloy is aged at500℃, temperature field plays a dominant role, the role of the current field is weak. The technology of aging with DC electric field can improve the peak of microhardness of the Cu-0.33Cr-0.06Zr alloy. The peak microhardness of the alloy aged at450℃for0.25h with400A·cm-2current field is227HV, exceeds206HV of the alloy aged without current field. The better overall performance of the alloy aged with dc current was conductivity reached79%IACS, microhardness reached210HV aged with300A·cm-2at450℃for0.5h. There was coherent face-centered cubic Cr-phases with lobe-lobe contrast existing in the alloy. Through the diffraction pattern calibration, There are CuZr3-particles, body-centered cubic Cr-phases and Cu4Zr-particles precipitates existing in the alloy aged, and the Cr-particles exhibited the N-W orientation relationship with the Cu matrix. According to the electrical conductivity changes in the aging treatment and the relationship between volume fraction of precipitates and time, the Avrami equation of phase transformation kinetics and the electrical conductivity equation at different current densities were obtained.