Research On The Substrate Deformation And Stress Control Of Thin-walled Ti6Al4V Parts By Laser Deposition Forming

Laser deposition forming technology is an advanced manufacturing technology that has been developed rapidly in recent years. It can quickly and directly produce densified metal components as the further development of the laser deposition technology. This technology can reduce production cost, shorten the manufacturing cycle, produce complex structural components which can’t or difficult to be formed by the conventional technology and also can repair the damaged parts.Since titanium alloy has many advantages, such as low density, high specific strength, strong ability of anti-corrosion, high temperature performance, etc., so that titanium structural parts have been widely used in advanced aircraft manufacturing. However, the manufacturing material utilization rate of titanium structural parts is extremely low, but with long development cycle, and high manufacturing cost. Manufacturing titanium alloy structural parts by laser deposition forming technology has become a hotspot around the world researchers now.In this paper, TC4 titanium alloy powder and plates were used as laser deposition material. The basic process of the laser deposition titanium alloy thin-walled parts, the deformation of the plates and the problem of deposition layer stress control were studied.Firstly, single-channel laser deposition experiments by different process parameters were performed both in YAG and CO2 laser.The influence of single channel deposition layer’s macro morphology was studied by laser power, scanning speed and powder feed rate. Orthogonal test method was used to analyze primary and secondary impact of the various process parameters on the size of macro-deposited layer. The forming properties of two kinds of lasers are compared. Using different observation and testing methods studied the influence of laser power and scanning speed parameters on the microstructure and microhardness of the laser deposition layer. The influence mechanism is analyzed. The laser deposition process parameters were optimized, which provided the basic process parameters for the deformation and stress control experiment of the laser deposition forming.In order to obtain the influence on matrix deformation by laser deposition forming process, single-layer multi-channel laser deposition experiments were preformed using optimized process parameters in different thickness of titanium alloy sheet metal parts and frame type parts. The deformation of the substrate and the distribution of residual stress were test. The deformation mechanism was revealed.Two methods, the ultrasonic peening and cold work hardening hammer, were used to control the stress after laser deposition. The influence on microstructure and hardness was studied using these two methods. By measuring residual stress of the deposited layer, the control impact of the two kinds of methods was comparatively analyzed.Based on the force control of deposition layer by ultrasonic peening and cold work hardening hammer, the titanium alloy frame parts was manufactured using the laser metal deposition. By observing the forming quality and testing the deformation of base sheet, the effect of two kinds of processing technology on titanium alloy parts laser deposition shaping was studied.