Study On Fatigue Performance Of TC4/TC11 Gradient Composite Materials By Laser Deposition

In this paper,TC4/TC11 titanium alloy composite structures were prepared by laser deposition manufacture technology.The microstructures of composite structures were observed and analyzed by OM,the microhardness and wear performance of each gradient layer was tested.The high-cycle fatigue life of two composite structures and each gradient layer were tested and analyzed.The results show that the hardness and wear performance of the material are continuously improved when content of the TC11 increases.The interface of the microstructure of the directly transited TC4/TC11 composite material is obvious,while the TC4/TC11 gradient composite with three transitional layers is not obvious and transitions uniformly from TC4 to TC11.The microhardness of 100%TC4,75%TC4,50%TC4 and 25%TC4 is 494HV_0.2,508HV_0.2,524HV_0.2 and 542HV_0.2,respectively,the wear mass loss is 6.2mg,4.2mg,2.9mg,and 2.7mg,respectively,and the coefficient of friction is 0.6,0.54,0.49,0.42.Existence of the gradient layer helps to improve the fatigue performance of TC4/TC11titanium alloy composite.The median fatigue life of the directly transited TC4/TC11 composite material under stresses of 550 MPa and 800 MPa is 2.01?10⁶,0.99?10⁵ cycles,respectively,while the median fatigue of the TC4/TC11 gradient composite with 3 transition layers under stresses of 550 MPa and 800 MPa is 4.61?10⁶,1.80?10⁵ cycles,respectively.The median fatigue life of each gradient layer increases with the increase of TC11 content.Fatigue fracture is an important basis for fatigue life analysis.The fatigue source is preferentially produced at the pores,fatigue strips and secondary cracks were generated during crack propagation,and generation of the secondary cracks have consumed a lot of energy,so that the main crack growth rate was slowed down,and thus improve the fatigue life of the material.The fracture morphology of the instantaneous fault zone is mainly composed of dimples.Under low stress,the dimples are small and shallow,and the dimples are large and deep under high stress.The TC4/TC11 gradient composite structure has broad application prospects in the manufacture of aircraft components.The composite structure is subjected to cyclic load during work.If the structure is fatigue-damaged,it will seriously threaten the safety of the aircraft and the pilot.Therefore,it is great practical significance to improve the fatigue performance of the structure.