Effect Of Cold Deformation And Heat Treatment On The Microstructure And Properties Of Cu-Cr-Ti(RE) Alloy

The effect of cold deformation before and after ageing treatment on the microstructure and properties of Cu-Cr-Ti (RE) alloys were studied. The microstructure and composition were characterized by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy. The ageing characterictics and the effect of size, morphology, distribution of precipitation phases on the properties of Cu-Cr alloy were investigated emphatically. The effect of these element additions on microstructure and properties of Cu-Cr alloy was discussed. The following conclusions can be drawn from above investigation:1. Cold deformation before ageing can improve the microstructure and properties of Cu-Cr alloy significantly. After ageing at 500℃for 2h and deformation, the grains are elongated along the direction of deformation, and the second phase Cr-rich phase is precipitated along the grain boundaries. At 60%, the uniform microstructure with sufficient precipitation of the Cr-rich phase is obtained. With increasing deformation, the discontinuous grain boundaries present and the secondary phase are aggregated in the grain boundaries. A good combination of properties can be obtained for Cu-0.3Cr-0.2Ti alloy. After 60%cold deformation and ageing at 500℃for 2h, and the hardness and electrical conductivity are 129Hv and 83%IACS, respectively.2. Dy and Y addition can improve the hardness and electrical conductivity of Cu-0.3Cr-0.2Ti alloy, but Dy addition is more favorable for the fine precipitation and uniform distribution of seconday phase. In comparison with Cu-0.3Cr-0.2Ti alloy, after 60%cold deformation and ageing at 500℃for 1.5h, the hardness and electrical conductivity of Cu-0.3Cr-0.2Ti-0.1Dy alloy are increased by 7.7%and 6.7%, respectively, while the hardness and electrical conductivity of Cu-0.3Cr-0.2Ti-Y alloy are improved 4.6%and 3%, respectively.3. Deformation has a remarkable effect on the properties of aged Cu-0.3Cr-0.2Ti-Dy and aged Cu-0.3Cr-0.2Ti-Y alloy. With increase of deformation, the hardness increases significantly while the electricial conductivity decreases obviously. A good combination of properties can be obtained after 40%deformation. Cu-0.3Cr-0.2Ti-0.1 Dy alloy has a hardness of 127Hv and an electrical conductivity, while the hardness and electrical conductivity of Cu-0.3Cr-0.2Ti-0.1 Y alloy are 123Hv and 68.1%IACS, respectively.