| Precipitation strengthening phase is distributed dispersedly in copper matrix ofprecipitation strengthening copper alloy after heat treated by solid solution and aging,thus the precipitation strengthening copper alloy can obtain high strength and goodconductivity at the same time. But it is difficult to further improve the syntheticalproperties of copper alloy by the traditional methods of solution and aging. This paperresearches mainly on precipitation strengthened Cu-Cr alloy, adopting heat treatmentprocess of solid solution, cold deformation and aging. DC electric current was appliedto Cu-Cr alloy in the process of aging. The effects of DC electric current on propertiesof Cu-Cr alloy were studied, and microstructure was observed. Phase transitionprocess and aging precipitation kinetics of the alloy were discussed through the changeof conductivity of the alloy during aging, and the effect of DC electric current on agingprecipitation phase change process of the Cu-Cr alloy was comparatively studied. Theinfluence of different current densities and aging temperatures on aging characteristicsof Cu-Cr alloy was systematically studied.The main conclusions were obtained:1. The influence of DC electric current on properties of Cu-Cr alloy during aging.(1) The influence of DC electric current on the maximum conductivity of the aged Cu-Cr alloy was not obvious. But DC electric current was found to promote the agingprecipitation rate of Cu-Cr alloy; the impact of electric current on the agingprecipitation rate was more obvious between6h and12h.(2) DC electric current canshorten the time for the aged alloy to reach maximal tensile strength, and slightlyreduce the peak of tensile strength. The electric current was thought to promote theprecipitation of the solute Cr atoms and the occurrence of the recovery, and thenenhance the precipitation strengthening and increase the degree of recovery, bothcombined action made the tensile strength of the aged Cu-Cr alloy with electricalcurrent differ from the case without current.(3) The hardness of the alloy with DC electric current was higher than that without current when the aged Cu-Cr alloy wasrolled under the same cold deformation.2. Microstructure of aged Cu-Cr alloy with and without DC electric current. DCcurrent was found to make precipitates smaller and uniformly dispersed, andstrengthen the precipitation degree of solute Cr atoms at high density of vacancies anddislocations. The precipitation sequence of precipitates aged with and without DCcurrent was identified as: Cu solid solution→Cr GP zone→coherent Cr phase(bcc)→incoherent Cr phase (bcc). The DC current was mainly thought to shorten thetime of enrichment of solute atoms and then transition to the GP zone.3. The phase transformation kinetics equation and the conductivity equation werecalculated. The curves of phase transformation kinetics and conductivity equation wereworked out, and the impact of DC current on the phase transition process of the alloywas analyzed. |
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