Microstructure and fatigue properties of TC4/TC11 gradient materials by laser deposition

Abstract:

In order to study the microstructure and fatigue properties of laser deposited TC4/TC11 gradient materials, directly transited and gradiently transited TC4/TC11 composite materials were prepared by laser deposition manufacturing technology. The microstructures of composite materials by different transition were observed, the fatigue properties of these two composite materials under stresses of 550 MPa and 800 MPa were tested, and fatigue fractures were analyzed. The results show that the interface of the microstructure of the gradient material with 3 transition layers is not obvious, and microstructures of TC4 and TC11 are integrated more tightly in the transition zone than that of the directly transition composite materials. The fatigue life of the gradient material with 3 transition layers under either stress is higher than that of the direct transition, which is relatively increased by 129.3% under low stress and 81.8% under high stress. The direct transition composite material cracks along the bunch of α-sheet during crack propagation, with a large sliding surface and a low fatigue life. The cracks of gradient material with 3 transition layers grow along a single α-sheet, the slip plane is small, and the crack propagation path is more tortuous, which improves the fatigue life.

Key words:laser deposition manufacturing; titanium alloy; gradient materials; microstructure; fatigue properties