| Upon the application background of high performance sliding electrical contact parts, the microstructures and properties of precipitation-hardened dilute solute Cu-Cr-Zr alloy were studied. The effect of heat treatment, especially aging treatment, on microstructures, mechanical and electrical properties, and sliding wear behavior of Cu-Cr-Zr alloy was discussed, in order to meet with the demand of sliding electrical contact wire with high strength, high conductivity and good wear resistance as well.The microstructures of specimens of solid solution and after aging treatment were systematically investigated by means of SEM, TEM and EDS. The morphological and structural aspects of precipitates and its formation mechanism were studied in detail. The characters of the alloy at different aging stages were surveyed, and the relationship between precipitation and aging treatments of the Cu-Cr-Zr alloy was then summarized. It was found that the age hardening of Cu-Cr-Zr alloy is the result of the initial homogeneous metastable precipitation of a complex intermetallic phase (Heusler phase) with a suggested composition of CrCu2(Zr,Mg) that decomposes thereafter into bcc chromium and Cu4Zr particles giving a finer dispersion. Aging at 500癈 for 1 h results in the formation of fine, dispersive and coherent precipitates within the copper matrix.The mechanical and electrical properties of Cu-Cr-Zr alloy after various heat treatments were investigated. The effect of heat treatment, including aging temperature, aging time and cold working before aging treatment, on the mechanical and electrical properties were studied and the optimal heat treatment condition was presented. It was found that Cu-Cr-Zr alloy aged at 500 癈 for 2 h shewed the optimal combination of high hardness and high conductivity. The cold working before aging treatment can improve the hardness of Cu-Cr-Zr alloy in a great extent while its electrical conductivity shows no significant drop. After optimal heat treatment, Cu-Cr-Zr alloy showed the integrated property with strength of 562.7MPa, hardness of 159.3(HV) and electrical conductivity of 80.57IACS%.The friction and wear behavior of Cu-Cr-Zr alloys dry sliding against a brass counterface were investigated on a MMW-1 pin-on-disk wear tester. The worn surfaces of the Cu-Cr-Zr alloys were studied by SEM and EDS. The microstructures of the subsurface area of Cu-Cr-Zr alloy after wear tests were also analyzed by TEM. The results indicated that the friction coefficients showed a general trend of decrease with the increase of normal load and sliding speed. The wear rate of the aged Cu-Cr-Zr alloy increased monotonically with the increase of the normal load. With increasing sliding speed, the wear rate of the aged Cu-Cr-Zr alloy decreased in the initial stage and then began to increase. After reaching the maximum wear rate, the wear rate decreased again with further increasing in the sliding speed. Adhesive wear and abrasive wear were the dominant wear mechanisms under unlubricated conditions. With high load and continuous sliding behaviors, the plastic deformation wasintensified and thus formed a layer with the fragmented microstructure and intensified plastic deformation zone in subsurface region.The electrical sliding wear behavior of Cu-Cr-Zr alloys against a brass counterface was investigated on a pin-on-disk wear tester. The worn surfaces of the alloys were also analyzed by SEM and EDS. The results indicated that wear mass loss of Cu-Cr-Zr alloy/brass both monotonically increase with increasing electrical current. Adhesive wear, abrasive wear and arc erosion were the dominant mechanisms during the electrical sliding processes. Under electrical current conditions, the aging treatments had an effect on the wear resistance of Cu-Cr-Zr alloy. At the constant current density, the wear rate of Cu-Cr-Zr alloy decreased with aging temperature, and reached the minimum at 500癈, then increased with further increasing aging temperature. Compared with commercially used Cu-Ag alloy wire (CTHA110) under t... |
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