Forming Mechanism And Properties Of Cu-Cr-Zr Copper Alloy In Selective Laser Melting

Cu-Cr-Zr copper alloy possesses excellent electrical and thermal conductivity,as well as high strength,hardness and high temperature performance,and has been widely used in machinery,electronics,chemical industry,transportation,aerospace and other fields.With the rapid development of the industry,the traditional Cu-Cr-Zr copper alloy forming method has been unable to meet the rapid development needs of emerging industries and national defense industries,especially for the copper alloy products with complex structures.Selective Laser Melting(SLM)has the ability to directly form dense and complex parts with high precision,which provides the possibility for the development and rapid forming of Cu-Cr-Zr copper alloy parts with complex structures.Therefore,this paper studied the processes and performances of the SLMed Cu-Cr-Zr copper alloy,systematically.Based on the study of the forming density,microstructure,texture,mechanical properties,surface quality,support technology,etc.,the influence of process parameters on characteristics and performance of the SLMed parts are analyzed,and a complete set of processing parameters and some important research results are obtained.Details are as follows:(1)The response surface method was used to investigate the basic forming parameters of Cu-Cr-Zr copper alloy in SLM,and the relationship model between processing parameters and forming density was established.It is found that the process parameters have significant effects on the density of Cu-Cr-Zr copper alloy,especially the laser power.The results showed that SLMed Cu-Cr-Zr copper alloy parts with high density can be formed under the process parameters of laser power of 370 W,scanning speed of 650 mm/s,and scanning space of 120?m.The corresponding density can be reached to 8.8761 g/cm~3 with the relative density(relative to wrought copper alloy:8.8761 g/cm3)of 99.43%.(2)The microstructure,texture,mechanical properties and anisotropy of Cu-Cr-Zr copper alloy fabricated by SLM were systematically studied.The top surface grains of the Cu-Cr-Zr copper alloy sample formed by SLM are mainly small equiaxed crystals;while the side grains are mainly long crystals with large aspect ratios,and the grains have obvious ductile growth along the processing direction characteristics.There is obvious texture in the Cu-Cr-Zr copper alloy formed by SLM,which is mainly manifested as the<110>direction of the crystal grains parallel to the building direction of SLM.The SLMed Cu-Cr-Zr copper alloy has a tensile strength(321MPa±7 MPa)equivalent to that of the wrought part(337 MP±7 MPa),and the elongation(25±1.1%)is significantly higher than that of the wrought sample(15±0.6%).The macro-mechanical properties of Cu-Cr-Zr copper alloy parts by SLM have obvious anisotropy that the mechanical properties of the formed samples in the 0°direction are better than the 45°and 90°directions.(3)The influence of processing parameters,such as top surface and side surface processing parameters,the surface quality of SLMed Cu-Cr-Zr copper alloy were studied.Defects such as balling phenomena,irregular melting tracks,and non-overlap of tracks are the main factors affecting the quality of the top surface.Remelting method can effectively improves the forming quality of the top surface;the profile scanning processing parameters have significant impacts on the quality of the side surface,by adjust which the quality of side surfaces can be improved.In general,under the condition of higher energy input,the fully melted metal powder of Cu-Cr-Zr copper alloy has an effective remelting and modification effects on the formed defects and a good surface quality can be obtained.The scraper has significant effects on the forming quality of the down surface of the Cu-Cr-Zr alloy.Under improper profile processing parameters,the edges of the down surface are prone to be warping,deformed and other defects(4)The SLM support processing parameters of Cu-Cr-Zr copper alloy has been systematically studied.A three-step development method of support processing parameter,preliminary selection of support forming characteristics,final selection of mechanical properties,and forming verification,was proposed.The SLMed Cu-Cr-Zr copper alloy limiting included angle between the suspended inclined structure and the horizontal direction is 50°.With the included angle decreases,the forming accuracy of the inclined structure loses significantly.The strength of the support sheet and tooth structures gradually increase with the increase of the line energy density.The tensile strength and fracture displacement of the support structures increase with the increasing of the laser power,decrease with the increasing of the scanning speed and decrease with the layer thickness increasing.The layer thickness has a significant impact on the processing window size.Comprehensively considering the support strength,support forming efficiency and the results of verification experiments,a series of support processing parameters are finally determined under the condition of 60?m layer thickness.(5)Based on the obtained processing parameters,dense Cu-Cr-Zr copper alloy lattice structures were manufacturesd by SLM,and their forming accuracy,mechanical properties,compression failure mode and microstructures are systematically studied.The reconstructed three-dimensional model of the lattice structure based on the macro-CT scan data is in good agreement with the designed model and the size deviations are within 0.1 mm.The metallographic structure of the lattice structure is similar to that of the bulk material,while the grain sizes are smaller.The compressive stress-strain curves of the Cu-Cr-Zr copper alloy lattice structures have obvious stress platforms without stress collapse.The elastic moduli and plateau stresses of the Cu-Cr-Zr copper alloy lattice structure increase significantly with the increasing of the volume fraction,while slightly increase with the increasing of the unit cell size.