Study On Forming Technology And Performance Of Stainless Stell And Titanium Alloy By Selective Laser Melting

Selective Laser Melting is one of the additive manufacturing which is widely used. It gets more and more attention of the society because of high manufacturing precision, complicated manufacturing structure and the personalization. In the field of medical and aerospace, 316L stainless steel and Ti-6Vl-4V alloy have a larger study space because of their excellent performance. However, the study on the microstructure and properties of the two-alloy forming process made by SLM is not perfect, The technology of defect controling is not yet mature. so the microstructure and properties of 316L stainless steel and Ti-6Al-4V alloy were studied in this paper. First, we studied the effects of defocusing and focus printing on the microstructure and properties of 316L stainless steel. Then, the influence of different hardness and compression properties of 316L stainless steel and Ti-6Al-4V alloy were investigated to determine the preferred SLM process parameters and heat treatment process, finally, it can provides technical support for 316L stainless steel and Ti-6Al-4V alloys for 3D printing applications. The main conclusions of this paper as follows:(1) Focus print is better than defocusing. Using different process parameters orthogonal test of focus print, the results showed that the optimum process parameters of 316L stainless steel as follows: the scanning interval S=0.05 mm, scanning speed V=1500 mm/s, scanning power P=450 W, In this process, the sample density reached 95.9%; then, the optimum process parameters of Ti-6Vl-4V alloy was the scanning distance S=0.07 mm, scanning speed V=2500 mm/s, scanning power P=450W; and in this process, the sample density of Ti-6Vl-4V alloy reached 98.1%.(2) The microstructure of SLM 316L stainless steel were mainly composed of fine equiaxial crystal and columnar crystal. The tensile strength was 645 MPa, the yield strength was 560 MPa,and the elongation was 45%. The tensile fracture appeared dimple, showing a typical ductile fracture.(3) The microstructure of 316L stainless steel presented a single austenite tissue after heat treatment, and with the increases of the temperature of heat treatment, the grain had growthed so that the fusion line have disappeared; The mechanical properties of the parts can be adjusted by heat treatment, under the temperature at 750? of the heat treatment for 2h and with the furnace cooling, it showed good tensile properties: the tensile strength was 680 MPa and the yield strength was 480 MPa; Under the heat treatment temperature at 1000? for 1h and with the furnace cooling, the elongation was achieve the best, was 56%.(4) The microstructure of SLM Ti-6V1-4V was mainly composed with acicular?'-martensite,and the tensile strength was 1250 MPa, the yield strength was 1160 MPa, the elongation was only 8%, and the fracture have tearing edges showing a quasi cleavage fracture; The compressive strength was 1755 Mpa and was higher than the tensile strength. The microstructure had an obvious change after heat treatment at 850?, there happened a marked coarsening, and changed more uniform,meanwhile, the tensile strength was 1010 MPa?the yield strength was 950 MPa and the elongation was 9.0%. There were many different sizes of dimples appered, so the plasticity enhanced.