Microstructure And Properties Of Point-mode Forging And Laser Additive Manufactured TC4

TC4 titanium alloy is also known as Ti-6Al-4V,which is a typical α+β titanium alloy.The microstructure of the traditional laser rapid forming parts is coarse columnar crystal,showing anisotropic properties,and the practical application conditions are harsh.In this paper,the point forging laser additive forging technology was applied to TC4 titanium alloy substrate,and the reduction amounts were 0.15 mm,0.20 mm and 0.25 mm,respectively,to study the microstructure and properties of the original formed parts.The microstructure,tensile properties,fracture morphology and microhardness of TC4 titanium alloy forgings with different reduction amounts were analyzed by solution aging heat treatment.The results show that:The macrostructure of point forging laser additive TC4 titanium alloy is equiaxed grains,and the intragranular microstructure is basketweave structure.With the increase of the reduction during the point forging process,the equiaxed grain size gradually decreases,and the length of the fine needle-like α phase inside the grain gradually decreases.The strength of the original TC4 titanium alloy forgings has been significantly improved,and the microhardness value has been increasing,but the plasticity cannot all meet the forging standard.After heat treatment,the equiaxed grains in TC4 titanium alloy undergo static recrystallization,and the grain boundary α phase appears fracture spheroidization.The lath α phase is coarsened,and the fracture spheroidization also occurs.At the same solution heat treatment temperature,the larger the reduction,the larger the equiaxed grain size,the higher the content of spheroidized α phase in the crystal,and the more obvious the coarsening of α phase.With the increase of solution temperature,the primary α phase decreases and the content of secondary α phase increases.The strength of TC4 titanium alloy after solution heat treatment is greatly improved compared with that of the original TC4 titanium alloy.The strength and microhardness of TC4 titanium alloy after solution treatment at 950 ℃ are the highest.