| CuCrZr alloy as an excellent conductive and thermal conductive material is widely used in manufacturing wire,radiator and other parts,mainly used in automotive,aerospace,electronics and other fields.Complex operating environment requires it not only to have excellent electrical and thermal conductivity properties,but also to have excellent mechanical properties and high temperature resistance.At present,the CuCrZr alloy parts produced by traditional manufacturing methods have been difficult to meet the requirements of complex working environment.Selective Laser Melting(SLM)is an important branch of additive manufacturing technology.It has the technical advantages of excellent forming performance and metal parts with complex structure.At the same time,it saves a lot of materials and has high forming efficiency.SLM technology provides a feasible scheme for the preparation of CuCrZr alloy parts with excellent comprehensive properties and highly complex structures,and extends its application range.Therefore,the forming process and properties of CuCrZr alloy fabricated by SLM were studied in this paper.The main research contents include the optimization of the SLM process parameters of CuCrZr alloy by combining numerical simulation and orthogonal test,and obtain CuCrZr alloy with high relative density and good mechanical properties.At the same time,the temperature field thermal behavior of CuCrZr alloy during SLM process,as well as the microstructure,phase composition and mechanical properties after forming were analyzed and discussed.In addition,the heat treatment process of CuCrZr alloy fabricated by SLM was optimized and its high temperature tensile properties were investigated.The specific research contents and main conclusions are as follows:(1)The numerical simulation model of SLM forming CuCrZr alloy was established by ANSYS APDL.The temperature field of SLM forming process was simulated numerically,and the morphology characteristics and heat transfer behavior of molten pool under different SLM process parameters were obtained.The results show that with the increase of laser power,the width and depth of the molten pool gradually increase,and the lap value of the adjacent molten channel increases,which leads to the enhancement of metallurgical bonding between layers and between the molten channel and the molten channel.Meanwhile,the existence time of the liquid molten pool increases and the cooling rate decreases.With the increase of the scanning speed,the width and depth of the molten pool gradually decrease,and the lap value of the adjacent molten channel decreases,which leads to the decrease of the metallurgical bonding between layers and between the molten channel and the molten channel.Meanwhile,the existence time of the liquid molten pool decreases and the cooling rate increases.(2)The effects of SLM process parameters on the density and mechanical properties of samples were studied.The results show that the optimal technology is the laser power of 330 W,scanning speed of 700 mm/s,scanning space of 90 μm and layer thickness of 30 μm.The relative density,hardness and tensile strength of CuCrZr alloys prepared by the SLM with optimal process are 99.78%,89.47±1.4 HV and 289.05 MPa,respectively.The microstructure of the top and side of CuCrZr alloy samples formed by SLM is obviously different,and the growth direction is along the processing direction.The growth direction of the top and side grain has a preferred orientation at <110>,and the microstructure has a strong {110} texture.(3)The effect of heat treatment on microstructure and mechanical properties of CuCrZr alloy was investigated.The results show that there is a small amount of fine precipitated phase in the grain of CuCrZr alloy formed by SLM,the composition of which is mainly Zr and the size is about 30 nm,while Cr element is not precipitated and is uniformly solidly dissolved in the Cu matrix.After different aging processes,there is no obvious change in the microstructure,and no coarse precipitates appear at the grain boundaries.More fine precipitates appear in the Cu matrix,which plays a precipitation strengthening role.The main component of Cr is about 40 nm,and a small amount of Zr phase precipitates around can inhibit the growth of Cr precipitates.The tensile strength and hardness of the samples reached the maximum value at 460℃ and held for 60 min,where the tensile strength increased to515.5±12.8 MPa and the hardness increased to 185.7±1.82 HV.(4)The temperature has a significant effect on the high temperature tensile properties of CuCrZr alloy after heat treatment.With the increase of tensile temperature,the tensile strength and the elongation of CuCrZr alloy show a decreasing trend.When the temperature is150℃,the tensile strength and the elongation of CuCrZr alloy are 394.72±2.66 MPa and6.37±0.61%.With the temperature rising to 200℃ and 250℃,the tensile strength decreased by 9.6% and 10.5%,respectively,and the elongation decreased to 3.79±0.21% and2.96±0.01%. |
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