Study On The Preparation Of Copper Single Crystal With Different Initial Orientations And Deformed Microstructure Of Cold-drawn

The ultra-fine copper wires actually used in practical application can usually be obtained after being cold drawn many times. The single crystal copper wire which produced by OCC method has relatived large initial diameter, and it also needs to be drawn several times.During drawing process, the deformed microstructure will be formed and have significant influence on the microstructure and physical properties of the copper wires after cold drawing. The initial orientation of single crystal copper wires will have a significant effect on the microstructure changes and physical properties. For getting good performances of copper wires, it is necessary to know the effect of the initial orientation of single copper wires on the microstructure evolution during drawing process. In the present work, the single-crystal copper samples with different initial orientations have been prepared by use of modified Bridgman crucible,the cold drawing microstructures of the single crystal copper samples with different initial orientations after different extent deformation have been studied by TEM and EBSD method. The micro hardness is performed by Vicker hardness tester measurements.The experimental results show that with the self-improved high-purity graphite Bridgman crucible and in the high vacuum condition, if the temperature is controlled at 1450±5℃, and the running speed is controled around 2μm/s, the single crystal copper samples with different initial orientation can be effectively prepared.The TEM results show that when the strains is 0.94, the initial orientation<111> and <110>single-crystal copper starting rotation of the orientation; when the strains are larger than 0.94, there are two kinds of microstructures. First is elongated dislocation cells in the longitudinal section and the second is equiaxed dislocation in the cross section. When the strains are larger than 1.39, the size of dislocation cells decreases as the strain increasing until they reach a critical minimum size. When the strain reaches to 1.96, the single crystal samples with initial orientitation<111> and<100> will have the trend to rotation of<100> direction.The EBSD results show that at low strains, the region where the drawn direction deviate from initial orientation to other crystal directions starts to appear at the surface of the samples, and with the strains increasing, the region will spread from the surface to the center; It is observed from the serial drawing process that<111> fiber texture component parallel to the drawn direction is in the centre of the samples and<100> fiber textent compoment is in the surface. The stabilility of deformation texture components is in the order of<111>,<100>and other texture. In the cold-drawing deformation process, the initial orientation of the samples will have an evident effect on the proportion of the deformation texture generation and distribution.The Vickers hardness measurement results show that among<100>,<110> and <111>three kinds of the original sample, the sample with<110> initial orientation has the largest micro-hardness values. As the strain increases, the sample with<100>and<110> will have relatively fast increase of the Vickers hardness value. When the strains are larger than 1.96, the microhardness values of the samples with all the three initial orientation will be basically in a same level.