| The traditional processing methods of jewelry have the disadvantages of low production efficiency,high cost of personalized customization,and it have been unable to meet the growing needs of mankind.The characteristics of rapid and personalized customization of additive manufacturing technology have brought unlimited creativity to jewelry processing.In this paper,Cu-10 Sn alloy and 925 Ag alloy are used as raw materials to study the forming process of the selected laser melting and to fabricate jewelry.In this paper,a study on forming process and properties of Cu-10 Sn alloy in SLM was carried out.The process parameters of density and dimensional accuracy of SLM-formed bronze alloys were optimized and analyzed by response surface methodology.The order of importance of factors affecting the density of SLM samples is : laser power > scanning speed > hatch spacing.When the laser power LP is 249 W,the scan speed SS is 181 mm/s,the scan pitch HS is 0.097 mm,and the layer thickness LT is 30 ?m,the optimal density of the formed parts is 99.36%.Meanwhile,The order of importance of factors affecting the dimensional accuracy of SLM samples is:scanning speed > laser power > hatch spacing,When the laser power LP is 250 W,the scanning speed SS is 740 mm/s,the scanning pitch HS is 0.07 mm,and the layer thickness LT is 30 ?m,the absolute error of the minimum size of the sample is 36.12 ?m.The roughness of the upper surface of the SLM sample is generally lower than that of the side.For the model with sharp Angle feature,the molding accuracy of vertical placement is higher.For the model of the circular hole feature,the molding accuracy of horizontal placement is higher.In addition,phase,microstructure,mechanical properties and heating processing of Cu-10 Sn alloy were further analysed and discussed in detail.The results show that the microstructure of Cu-10 Sn alloy fabricated by selective laser melting is mainly composed of ?-Cu phase and metastable phase??(Cu13.7Sn).Compared with the raw powder,the content of metastable phase ?? increased significantly.The average Vickers hardness values of the horizontal and vertical cross sections of the SLM samples were 158.2 ± 3.2 HV and 144.7 ± 3.4 HV,respectively.Compared with the Cu-10 Sn alloy obtained by hot-press sintering,the yield strength and tensile strength of the Cu-10 Sn alloy formed by SLM are 45% and 25% higher,respectively,but the elongation has a certain decrease.Compared with the SLM sample,the yield strength and tensile strength of the SLM sample after heat treatment have decreased,while the elongation has been significantly improved.For example,when the heating temperature of the heat treatment is increased to 600 ?,the average yield strength and average tensile strength of the sample decrease to 364 MPa and 572 MPa,but the elongation increases to29.11%.Previous researches have shown that the reflectivity of metal alloy powder has a significant effect on the forming performance of SLM.Therefore,the Cu-10 Sn powder was oxidized and its reflectivity was studied in this paper.It was found that with the extension of oxidation time,the reflectivity of copper alloy powder after oxidation treatment was significantly reduced.Meanwhile,SLM forming properties of Cu-10 Sn alloy powder after oxidation were studied.The results show that due to the increase of oxygen content,compared with the original powder,the maximum density of the sample prepared by oxidizing powder was relatively low,about 98.12 %.With the increase of the scanning speed,the powder adhesion phenomenon on the side of the SLM sample has been reduced to a certain extent,and compared with the original powder,the powder adhesion phenomenon on the side of the SLM sample prepared by the powder after oxidation treatment has been significantly reduced,and the side of SLM sample is only Some scattered powder particles adhered.With the increase of powder oxygen content,the sample size error showed an overall decreasing trend.With the increase of powder oxygen content,the sample size error showed an overall decreasing trend.At last,SLM forming properties of 925 silver alloy were studied in this paper.The differences of powder characteristics between cu-10 sn alloy powder and 925 Ag alloy powder were analyzed,and the process optimization and performance of 925 Ag alloy are studied.According to the powder performance test results,it can be found that although Cu-10 Sn and 925 Ag powders have little difference in average particle size,the flowability and bulk density of 925 Ag alloy powders are better.However,the reflectivity of 925 Ag alloy powder is about 64.68%,which is 70% higher than that of Cu-10 Sn alloy powder.The optimized densification of 96.76% for 925 Ag alloy is obtained using the parameter set of laser power 664 W,scanning speed 556 mm/s,hatch space 0.044 mm and layer thickness0.02 mm.In the case of constant scanning speed and scanning pitch,the absolute error of sample size decreases with the decrease of laser power.In the case of constant laser power and scanning pitch,the absolute error of the sample size increases with decreasing scanning speed.When the laser power is 300 W,the scanning speed is 400 mm/s and the scanning distance is 0.06 mm,the minimum size error of the sample is 108 ?m.The hardness of the925 Ag alloy sample on the horizontal section(106.4 ± 2 HV)is significantly greater than its hardness on the vertical section(90.1 ± 4 HV). |
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