Investigation On Preparation And Microstructure And Properties Of High Strength And High Conductivity Cu-Cr-Zr Alloys

The high strength and high conductivity of copper alloy are two contradictory properties.How to ensure the high conductivity of copper alloy and improve its strength is a technical problem in the field of high strength and high conductivity copper alloy.At present,microstructure ultrafine and nanocrystalline are considered as feasible ways and research hotspots to obtain high strength and high conductivity copper and copper alloys.The object of this study is CuCrZr alloy.The influence of different initial state of base metal on the processing effect of friction stir machining was investigated.By changing the processing parameters and cooling methods,the evolution law of the structure of the processing zone under various conditions was studied.The tensile properties and resistivity of CuCrZr alloy were measured under different processing conditions.The results provide theoretical support for new methods of preparing CuCrZr alloys with high strength and conductivity.It is found that the pre-deformation of the base metal can effectively increase the equivalent strain of the metal in the processing zone,and then promote the refinement of the structure in the processing zone.The microstructure evolution process of the processing zone is as follows: under the action of strong pressure-shear deformation,dozens of nanometer wide shear band structures are formed.These micro-shear bands are divided into fine sub-crystalline structures by high density dislocation walls under the action of rheological stress and dynamic recovery.The sub-crystals gradually change to large angle grains under the coupling of heat and force.By comparing the structure and properties of CuCrZr alloy obtained under different cooling methods,it is found that when the CuCrZr is FSP by stirring without shaft shoulder,the dislocation motion is hindered by solute atoms and precipitation phase.The dynamic recovery is inhibited and the temperature is increased.By using the FSP method without axle shoulder,the effective refinement of ultrafine CuCrZr alloy requires not only higher equivalent effect but also a certain temperature.As a result,when the rotating speed of the stirring needle is increased to 1200 rpm(not only the equivalent effect change but also the heat production),the microstructure and properties of different samples are obviously improved.Whether precipitate phase is precipitated in advance has a great influence on the microstructure and properties of CuCrZr alloy after processing.Precipitated phase before processing can make the alloy obtain better forming effect during processing and better strength,plasticity,hardness and electrical conductivity after processing?However,the precipitation of precipitated phase in advance will affect the homogeneity of precipitated phase and cannot effectively prevent the grain growth in the final aging treatment.Compared with the precipitation of precipitated phase after processing,its strength decreases.The precipitation phase after processing can not only prevent the precipitation phase from hindering grain refinement,but also improve the volume fraction of the fine dispersed precipitation phase and inhibit the grain growth in the aging process.The optimal processing path is: solid solution rolling(Air cooling,1200 rpm speed and 20 mm/min speed)FSP 450 ? aging treatment;the best performance matching is:806 MPa tensile strength,241 HV average hardness and 76.6 % conductivity excellent combination.