Research On Microstructures And Properties Of TC11 Forgings Repaired By Point Forging And Laser Reparing

As a thermally strongα+βtitanium alloy with excellent comprehensive properties,TC11 titanium alloy is widely used in aerospace and other fields.In this paper,the Point Forging and Laser Repairing(PF-LR)technology is used to repair TC11 rolled parts,and different heat treatment processes are carried out on the repaired parts.The research method of this article by contrast experiment,systematically expounded and analyzed the changes of microstructure,microhardness and uniaxial tensile mechanical properties of TC11titanium alloy before and after heat treatment by PF-LR.Firstly,the traditional laser cladding repair technology and the PF-LR technology were used to repair the TC11 titanium alloy samples respectively,and the microstructure of different areas was observed and analyzed.The results show that when the heat treatment temperature is higher than 650℃,theαphase in the repaired zone will be coarsened and spheroidized in varying degrees.When the heat treatment temperature is higher than 900℃,theα_G phase in the equiaxed grains will be broken.The microstructure in the heat-affected zone transitions from basketweave to equiaxed structure as the distance from the repair zone is farther.Equiaxed structure is distributed uniformly in the substate.Secondly,heat treatment experiments of different temperatures were carried out on the PF-LR TC11 titanium alloy repair samples.The results showed that the heat treatment temperature higher than 650℃would cause the originalαphase in the repair zone to have different degrees of coarsening and spheroidization.When the heat treatment temperature is higher than 900℃,the equiaxed grain boundaryαphase is disconnected,and the lathαphase of the equiaxed structure boundary of the heat-affected zone increases with the higher the annealing temperature,the larger its volume fraction and size.Finally,the mechanical properties of TC11 samples in the original state and u nder different heat treatment processes were tested.The results of microhardness te st show that the micro-hardness of the original state whole repaired samples increa ses from the substrate area to the repaired area,and the whole micro-hardness afte r heat treatment is higher than that of the original state except the aging group of980℃/2h/AC+530℃/6h/AC has the lowest micro-hardness.The test results of uniax ial tensile mechanical properties at room temperature show that the longitudinal poi nt forging laser repaired tensile specimens fracture in the substrate zone,and the p lasticity and tensile strength are lower than those in the substrate zone and the rep aired zone,and the fracture mode is quasi cleavage transcrystalline fracture.The fr acture position of the transverse PF-LR tensile specimen is in the middle of the w hole tensile specimen,and the tensile strength of the whole specimen is greatly im proved compared with that of the substrate due to the strengthening of the repaired area to the substrate area.The fracture mode is a mixed fracture mode of dimple fracture and quasi cleavage fracture.However,the tensile mechanical properties of the transverse and longitudinal tensile specimens after heat treatment are lower than the original state.