The Interface Structure And Performance Control Of LMD Forming Complex Structure On TC4 Titanium Alloy Forgings

Laser melting deposition(LMD)is an advanced manufacturing technology developed on the basis of rapid prototyping technology and laser cladding technology.His main principle is to use laser to focus on the surface of the substrate to form a molten pool,and then send the powder to the focus point of the laser and the substrate through the powder feeder.The molten matrix and the liquid metal powder combine with each other.As the laser moves,the molten metal rapidly cools and solidifies into a deposition layer.Although LMD technology has the advantages of high material utilization,free molding without mold,short cycle,low cost,and composite manufacturing between different materials,it still has the disadvantages of high manufacturing cost and low molding efficiency in the manufacturing of large batch or large parts.Especially in the field of Aer onautics and Astronautics,such as the deep space exploration sealed cabin,the engine shell of strategic missile,the main bearing frame of new aircraft and other large-scale key parts have some complex structures,such as thin-walled high rib,hollow shell,special-shaped lug,etc.,and the forming and manufacturing efficiency of LMD technology is low.Compounding additive manufacturing with traditional manufacturing is an effective way to manufacture such parts with high efficiency and low cost.Therefore,it is very important to study the interface structure and performance control of LMD forming complex structure on TC4 titanium alloy forgings.In this paper,a 6000 Wfiber laser is used to fabricate LMD on TC4 titanium alloy forgings.The effects of laser power,scanning speed and powder feeding speed on the surface morphology,melting height and melting width of the deposition layer were analyzed by using the orthogonal experiment of three factors and four levels.Then the best technological parameters of single laser melting deposition were obtained.Then,the multi-channel laser melting deposition experiment was carried out by changing the lapping ratio to find the best lapping ratio.Then,by using the best technological parameters and the best lap ratio of single channel laser melting deposition,the TC4 titanium alloy for ging substrate which has been treated with different surface roughness is manufactured by laser deposition,and the tensile specimen is prepared.By analyzing the macro morp hology,melting height,melting width and microstructure of TC4 titanium alloy single channel laser deposition structure under different surface roughness and different preheating temperature The effects of different surface roughness and preheating temperature on the microstructure and mechanical properties of the complex structure formed by LMD on TC4 titanium alloy forging were obtained.Secondly,by changing the laser power,powder disk speed and scanning speed of the best process parameters,the first several layers of laser melting deposition printing were carried out on the LMD forming complex structure of TC4 titanium alloy forging,and the tensile test bar was prepared.The micros tructure observation and mechanical property test were carried out on the LMD forming complex structure of TC4 titanium alloy forging was obtained by analyzing the experim ental results The best process parameters of the first several layers of the line.Finally,different heat treatment process tests are designed to explore the influence of solution a ging treatment and stress relief annealing treatment on the interface structure and perfor mance of LMD forming complex structure on TC4 titanium alloy forging,and the micr ostructure observation and mechanical property tests are carried out to analyze the influence of different heat treatment degrees on the interface structure and performance of LMD forming complex structure on TC4 titanium alloy forging,and the influence of different heat treatment degrees on the interface structure and performance of LMD forming complex structure with sink The best heat treatment process was obtained by comparing the accumulated state.