| Cu-Cr-(Zr)alloy has many excellent properties and is widely used in fields such as vacuum contacts,resistance electrodes,high-speed train contact line and aerospace materials.However,in recent years,various fields have put forward higher requirements for the performance of CuCr-(Zr)alloy,and the Cu-Cr-(Zr)alloy prepared by traditional methods can no longer meet the application needs.Selective laser melting(SLM)technology,which has many advantages,has been widely concerned.Its rapid solidification process can refine grains and suppress segregation,providing a possibility for developing high-performance Cu-Cr alloy materials.Therefore,in this paper uses Cu-25 wt.%Cr(Cu-25Cr)powder obtained by low-energy ball milling as the forming material to optimize and analyze the key process parameters of SLM forming.Based on the optimized process parameters,Cu-24Cr-1Zr alloy was prepared by adding a small amount of Zr powder,and the effect of Zr addition on the densities,organization and properties of the alloy was investigated,and finally the properties of the sample parts were improved by aging treatment.The specific research contents are as follows:(1)Using orthogonal experimental design method,the influence of important process parameters of SLM forming on the relative density,microstructure and mechanical properties of Cu-25 Cr alloy specimens was studied.The results showed that laser power was the main influencing factor on the Cu-25 Cr alloy density and microhardness.By optimizing the laser power,the optimal process parameters for SLM forming of Cu-25 Cr alloy were obtained: laser power of 350 W,scanning speed of 400mm/s,and scanning spacing of 0.1mm.The Cu-25 Cr alloy specimens prepared by the optimal SLM process parameters had relative density,microhardness,tensile strength and yield strength of 99.29%,197.51 HV,717.18 MPa and437.81 MPa,respectively.Microstructure analysis revealed that the rapid cooling characteristic of SLM technology greatly suppressed the coarsening and segregation of Cr phases,and the microstructure exhibited extremely small grain size and uniform distribution without obvious segregation(2)Based on the optimized process parameters for Cu-25 Cr alloy,Cu-24Cr-1Zr alloy samples were prepared at different scanning spacings.The results showed that the density and mechanical properties of the alloy samples gradually increased with the decrease of the scanning spacing.The addition of Zr improved the density and mechanical properties of Cu-24Cr-1Zr alloy compared with the SLM-formed Cu-25 Cr alloy.When the scanning spacing was0.09 mm,the density,microhardness,tensile strength,and yield strength of the SLM-formed Cu-24Cr-1Zr alloy reached 99.42%,228.12 HV,741.67 MPa,and 476.33 MPa and 12.71%,respectively.Microstructural analysis found that the addition of Zr significantly refined the Cr particles,further promoting the uniform distribution of the Cr phase.The primary Cr phase was dispersed on the copper matrix in the form of small spherical particles with a size of about300 nm,which increased the fine crystal strengthening effect and significantly improved the performance of the Cu-Cr alloy.(3)The SLM-formed Cu-24Cr-1Zr alloy was subjected to direct ageing heat treatment at different temperatures.The results show that with the increase of aging temperature,the microhardness and mechanical properties of the alloy gradually increase,and the precipitation effect of the alloy is best after aging treatment at 550℃,and the microhardness and strength increase more obviously,the microhardness,tensile strength and yield strength are 286.88 HV,905.63 MPa and 706.21 MPa respectively,which are 25.76%,22.11% and 48.26% higher than those before aging. |
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