| Cu-Cr-Ti alloys and Cu-Cr-Ti in-situ composites were prepared by medium frequency induction melting method and vacuum induction melting method in this paper. Study on the microstructure evolution and thermal stability of Cu-Cr-Ti alloys and composites after cold drawing and heat treatment was carried out. The effects of extrusion, solution treatment, cold drawing, intermediate annealing and ageing treatment on the properties of Cu-Cr-Ti alloys, such as tensile strength, electrical conductivity and softening temperature, were investigated by conductivity tests and room temperature tensile tests. By means of X-ray diffraction analysis, scanning electron microscope, energy spectrum analysis and optical microscope, the microstructure and the morphology, distribution of second phases were studied. Meanwhile, the microstructure, thermal stability, phase constituent, morphology and distribution of Cu-Cr-Ti in-situ composites which were prepared by directional solidification were investigated by the same analysis methods.The research results show that,with the increase of the drawing strain,longitudinal grain of Cu-Cr-Ti alloys developed into fibrous, while horizontal grains deformed irregularly, the tensile strength increased and the conductivity decreased. After the process of annealing, the tensile strength decreased, while conductivity increased. The Cu-0.53Cr-0.11 Ti, Cu-0.33Cr-0.05 Ti, Cu-0.53Cr-0.05 Ti alloys reach the highest tensile strength and conductivity after ageing at 400℃ for 2h. The tensile strength and conductivity of the above three kinds of alloy respectively reach to 73.2%IACS and 640 MPa,83.1%IACS and 590 MPa, 78.6%IACS and 623 MPa. The peak-ageing alloy of Cu-0.53Cr-0.11 Ti, Cu-0.33Cr-0.05 Ti, Cu-0.53Cr-0.05 Ti was kept under 470℃~545℃ for 30 minutes to evaluate softening resistance, and the corresponding softening temperature were respectively 530 ℃, 545 ℃, 530 ℃, reaching the requirement of the contact wire materials softening temperature,which is 500℃.With the increase of deformation, longitudinal structure Cr phase in Cu-11Cr-0.85 Ti directional solidification composites developed into fibrous structure,the fiber width-to-thickness ratio of horizontal structure Cr phase increased, irregular bending and twisting. The local fine fiber structure of deformation of Cu-11Cr-0.85 Ti directional solidification composites were fused and spheroidized. Some tiny fibrous structure formed ball chain along the direction of deformation. We found the thick fibrous structure does not take place obvious coarsening phenomenon. The longitudinal section of alloy could be observed complete fibrous structure, the fiber is relatively stable, So we can know the thermal stability of deformation of Cu-11Cr-0.85 Ti in situ composites is excellent. |
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