| With the development of the aerospace industy,the small thruster for attitude and orbitcontrol is increasily demanding, and models product is getting better and faster. Suchdisadvantages, as long manufacture cycle in injectors and poor welding performance withcombustion chamber, have restrained the performance and speed development of thruster forattitude and orbit control. In this paper, SLM is adopted to make injectors, with theassumption of in-situ welding injectors while making combustion chamber by CS. For thispurpose, the paper presents the basic research about SLM on Ti6Al4V and CS in situ weldingtechnology.The paper makes a systematic and thorough research and study on SLM of Ti6Al4V,densification mechanism and numerical simulation for temperature field, to improve theforming quality and density of SLM titanium alloy parts. On that basis, titanium alloy ring isselected as matrix material, Ti-C-Al as solder, in the study of the impact on performance ofTi6Al4V titanium CS joining quality from igniting method, compact density and Al content,along with the study about Ti-C-Al CS thermodynamics, macrokinetics and Ti6Al4V titaniumCS welding mechanism.The main results of this paper are included below:(1)To form titanium alloy parts, Nd:YAG laser with wavelength of 1064nm is chosen,installed with mechanical transmission system and shielding gas system.(2)To examine the influence mechanism to sample density of Ti6Al4V SLM frompowder properties and process parameters. Ti6Al4V powders show a narrower granularitydistribution, not in fovor of the densification of powder bed, therefore, the powder spreadingdensity is improved close to 70% after the gradation design of Ti6Al4V powder at thedimension ratio of 0.1; since energy density has a great impact on the compact density of finalsamples, laser power density is required to go beyong 10~6W/cm~2to guarantee metallurgybonding and smple compact density; the thickness of titanium forming layer is confirmed as0.1mm, according to the depth of laser transmission and powder performance.(3)To make a systematic study of the impact on titanium forming characteristic and density from process parameters (laser power, scan speed, scan strategy and scan space), bysingle tracks, thin layer multi-track and bulk SLM formation experiment. As a result, the bestscan strategy of Ti6Al4V titanium powder is refilling scan strategy with bi-directional scan;the best process parameters: laser power is 400W, overlapping rate 1 and the scanning speed750mm/min. To analyze the mechanical properties of Ti6Al4V powder SLM samples—lower tensile strength and better hardness, compared with that of traditional Ti6Al4V alloy.(4)To build mathematical model about forming process of Ti6Al4V powder by finitedifference method, based on which a emulate software is programmed, and the temperaturefield simulation of single tracks and thin layer multi-track comes into being. The curves of theactual temperature and simulating temperature are coincident through the firing test ofmeasuring temperature below the surface of powder in 0.1mm. The further scanning of singletracks and thin layer multi-track indicates: with the increasing of scanning velocity, thebreadth and depth of melting pool is decreased, and the highest temperature of melting pool isdown significantly; temperature incubation effect is minimum by refilling scan strategy withbi-directional scan.(5)To study the impact on performance of Ti6Al4V titanium CS joining quality fromigniting method, compact density and Al content. By comparision, the temperature in welds isas high as 1539℃under thermal explosion and pressure; there is an obvious transition regionin welding interface and the shearing strength is 68.33MPa; the compact density affect CSwelding significantly—compact density increases improve joint performance, however, toohigh compact density will aggravate heat loss, degrade joint performance even worse, so thesuitable compact density is around 60%; A1 content make a big difference to the grain size ofcompact synthetic product and joint performance—40% A1 content will densify CS reactionproduct and improve joint performance.(6)To make the profound research about Ti-C-Al CS thermodynamics andmacrokinetics, based on which the macrokinetics model is built.(7)To analyze the Ti-C-Al/Ti6Al4V interfacial concentration field according to theequation of interfacial concentration field, verified by the analysis results of interfacial energydispersive spectrum. Furthermore, the paper illustrates the formation mechanism of phaseconstruction in interface region and builds CS welding interface element diffusion andsolid-state reaction model. In brief, the paper proves the feasibility of integral and rapid process of ceramic-metalcomplex components by SLM+CS welding forming technique. SLM is used to make compactforming parts, 95.57% in density, which lays an experiment foundation for forming complextitanium alloy parts. CS is also used to weld Ti-C-Al intermetallics and titanium dissimilarmaterials, getting stronger shear strength of joint and proving the feasibility of the selectedmaterial technology, the designed components and the adoped methods. For the first time, thepaper studies the microstructure of Ti-C-Al intermetallics and titanium CS welding interface,the diffusion mechanism of alloying elements as well. The conculsion and research results canbe a solid foundation for further research on dissimilar materials CS welding.
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