| In this paper,single crystal copper material is used as the research object.The single crystal copper is connected by cold pressure welding in order to achieve effective connection and minimize the loss of the conductivity of single crystal high purity copper.The effects of compression and post-weld heat treatment on grain structure,grain orientation,grain size and texture change,as well as mechanical properties and electrical conductivity of cold-welded joints were investigated.The main results were obtained as following:When the amount of compression is constant,a plurality of finely oriented grain structures and deformation band structures appear at the joint interface in the axial direction of the joint.The deformation zone and the base metal zone still maintain a single crystal structure,and a small amount of fine grain structure appears in the deformation zone near the joint interface,and the base material zone undergoes directional rotation under the action of shear force.The strongest point of the base material region is concentrated on the {111} crystal face family;the strongest point of the deformation zone appears on the crystal face rotated about 10° clockwise around TD;At the interface of the joint,the texture is significantly weakened and the distribution tends to be uniform.The orientation of the base metal region is mainly concentrated near {111}<110>;the texture orientation of the deformation zone is the same as that of the base metal;and the interface area of the joint is formed with a weaker {111}<112> texture.As the amount of compression increases,the proportion of recrystallization at the interface increases first and then decreases,and the grains gradually become finer and have different orientations.The tensile strength of the joint increases first and then decreases with the recrystallization ratio.The strongest orientation of the crystal plane at the interface is first segregated in the {101} crystal family,and the strong orientation is changed from {101} to {111}.The density of the pole density increases slightly after a sharp decrease,and the texture strength also decreases first and then increases.When the amount of compression is small,the single crystal copper orientation mainly gathers near {2(?)51}<2(?)1(?)1> and{2(?)52}<1(?)2(?)4>.As the amount of compression increases,the orientations clustered around { 2(?)51}< 2(?)1(?)1> and{2(?)52}<1(?)2(?)4> disappear and become {111}<112> textures.then the {111}<112> texture gradually migrates to the {001}<110> texture and finally concealed in {111}<110> texture.The increase in the number of large-angle grain boundaries exacerbates the scattering effect of the grain boundaries on electrons,resulting in a slight decrease in conductivity.Under the same amount of compression,a cold-welded joint was subjected to a stress-relieving annealing process(300 ° C,holding for 2 h,cooling with the furnace).During the heat treatment,the atomic diffusion capacity is increased,and many fine crystal grains are recrystallized to form coarse grains having different orientations.Due to static recovery and recrystallization,the hardness of the deformation zone is significantly reduced,and the tensile strength of the joint exceeds that of the base metal.The electrical conductivity of the single crystal copper cold-welded joint was not significantly affected,and it could reach 99.24% of the base metal.Since the influence of the interface region on the conductivity is small relative to the size of the entire joint,the conductivity of the joint does not change significantly compared to the base material.Therefore,it can be considered that the cold pressure welding can achieve an effective connection to the single crystal copper,and the physical properties of the joint are more excellent after the heat treatment. |
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