Study On Partial Protection Of Laser Deposition Manufacturing TA15 Titanium Alloy In Inert Gas

Laser Deposition Manufacturing(LDM)is the manufacture of solid parts by in-situ melting of alloy powder which was used as a raw material by high-energy density laser and rapid solidification of molten alloy powder and deposition layer by layer.Unlike other conventional machining processes,LDM accordingly offers a wide range of advantages such as net-shape fabrication without the need of expensive moulds and special fixture which can greatly reduce the lead time for production and achieve high mechanical components.However,in the manufacture of titanium alloy parts,inert gas protection is the key to ensure organization and mechanical properties of titanium alloy powder,because it has tendency of high oxidation and nitridation in the molten state.In this paper,the inert gas protection of TA15 titanium alloy by laser deposition was studied.In this paper,the inert gas protection during laser deposition is studied.Firstly,The influence of adding the vertical blowing curtain on the powder aggregation of laser head for Laser coaxial feed powder was simulated by the FLUENT finite element analysis software.Additionally,the inert gas partial protection device was set up.The simulated results showed that the powder aggregation is good when the longitudinal air pressure was 0.5MPa,and forming a better forming quality while improving the powder utilization by laser deposition manufacturing in the convergence area from the following 10 mm of the focus to the focus.Secondly,the influence of the oxygen content in the forming atmosphere on the microstructure and mechanical properties of the deposited titanium alloy was studied.The experimental results show that the microstructures of the deposited and annealed are typical basket organization at different oxygen contents.With the increase of oxygen content,the yield strength and tensile strength of the alloy increase gradually,while the elongation and the shrinkage rate of the section decrease with an overall downward trend.the comprehensive mechanical properties of the alloy are better when the oxygen content is kept below 5 × 10-5.The fracture mechanism of fracture morphology also changes from ductile fracture to semi-cleavage semi-ductile fracture with increasing oxygen content.The hardness of the annealed state is slightly lower than that of the deposited state.With the increase of the oxygen content,the annealed state and the deposited state hardness are gradually increased.Finally,the microstructures,tensile properties and fracture morphology of TA15 titaniumalloy were investigated by laser deposition of local and total protection in inert gas.The results show that the tensile strength of local protection is higher than the overall protection,but the plastic is much lower than the latter.The anisotropy of microstructures and mechanical properties of different sampling direction of the deposited and annealed samples under two protection modes are investigated.The experimental result shows that anisotropy of mechanical properties varies at different sampling direction,this result could be attributed to the difference in the number of grain boundaries and grain boundary intensities in the deposition direction and the vertical deposition direction...