Papers by Keyword: Cu-Cr-Zr-Y Alloy

Abstract: The aging behavior of Cu-0.39Cr-0.11Zr-0.12Y alloy was investigated in this paper. The results showed that the tested alloy could obtain higher electrical conductivity and microhardness in solution at 960 °C for 1 hour under various deformations and aging at 480 °C condition than that of the alloy in solution-aged condition. The strength of the tested alloy increased with the increased deformation by cold working, the highest tensile strength value reached 637 MPa, while the elongation and electrical conductivity dropped a little. The values of tensile strength, electrical conductivity and elongation were 603 MPa, 79.66%IACS and 9.8% respectively when the second pulling deformation increased to 75.0%, that would meet the requirement of contract wire used in electrical high-speed railway.

Abstract: The degassing and dedusting mechanism of La and Ce during non-vacuum melting process of Cu-Cr-Zr alloy were analyzed by thermodynamics. The gibbs free energy changes of reactions of La and Ce with some impurties such as O2, H2, S, P and Si, were calculated to discriminate the possibility of reaction during the melting process, respectively. In addition, the effect of La and Ce on microstructure and properties were studied. The results show that La and Ce can react with O2, H2, S, P and Si, which improves the effect of degassing and dedusting remarkably; the addition of La and Ce can eliminate pine-tree crystal, fine grain and clear grain bourdary.

Abstract: High strength zinc-coated steels are used for automotive applications when high corrosion resistance and weight reduction are required. Resistance spot welding is the main method to assembly auto body. Steel sheets are held together under pressure exerted by copper alloy electrodes which concentrate welding current and clamp the sheets together. But welding of high strength coated steels reduces the electrode life. Even if electrode deterioration is a well-known problem, the understanding and modelling of the complex deterioration modes at different regions of the electrode is still limited. Developing a comprehensive thermo-electrical-metallurgical-mechanical model that describes the sequential deterioration is thus lacking. This work is a preliminary study which specifically addresses microstructural evolution modelling in age hardened CuCr1Zr electrode alloy. Evolution of precipitation is simulated using two models: a Johnson-Mehl-Avrami-Kologoromov model and the Myhr and Grong model. In both cases a calibration procedure based on hardness data was involved. Short isothermal heat treatments were used to develop a ‘master curve’ which captures the precipitate evolution. Preliminary results about the comparison of the two models are presented.

Abstract: The hot deformation behavior of Cu-0.35Cr-0.15Zr (wt.%) alloy was investigated by hot compression tests using a Gleeble-1500D thermal simulator system. The tests were performed under the conditions of 700°С- 820°С temperature and 0.01-10s-1strain rate. The results show that the flow behavior of the studied alloy could be described by the hyperbolic sine constitutive equation, and an active energy of 597.53 kJ/mol was calculated. The processing maps were obtained and analyzed according to the dynamic materials model. The optimum processing parameters of hot deformation of this alloy in the range of this experiment can be attained by the maps. The hot deformation temperature was 800-820°C and the strain rate was 0.01-0.1s^-1.The instability zones of flow behavior can also be recognized by the maps.

Abstract: A direct current was imposed during the ageing treatment of cold worked Cu-Cr-Zr alloys. The effect of increasing current density and ageing time on the electrical conductivity and microhardness has been investigated. The electrical conductivity was found to increase by about 22% IACS to a maximum value of 90% IACS. Furthermore, the microhardness increased by 21 HV up to 176 HV. A number of Cr precipitates and Cr-rich clusters were observed after the ageing treatment with direct current. The direct current was found to significantly enhance the efficiency of precipitation which is most probably due to the electron wind force and the electromigration-induced mass transport.