Microstructure and mechanical properties of laser additive repaired Ti17 titanium alloy
(1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China;
2. Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design, Ministry of Industry and Information Technology, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: Laser additive manufacturing technology with powder feeding was employed to repair wrought Ti17 titanium alloy with small surface defects. The microstructure, micro-hardness and room temperature tensile properties of laser additive repaired (LARed) specimen were investigated. The results show that, cellular substructures are observed in the laser deposited zone (LDZ), rather than the typical α laths morphology due to lack of enough subsequent thermal cycles. The cellular substructures lead to lower micro-hardness in the LDZ compared with the wrought substrate zone which consists of duplex microstructure. The tensile test results indicate that the tensile deformation process of the LARed specimen exhibits a characteristic of dramatic plastic strain heterogeneity and fracture in the laser repaired zone with a mixed dimple and cleavage mode. The tensile strength of the LARed specimen is slightly higher than that of the wrought specimen and the elongation of 11.7% is lower.
Key words: laser additive repair; Ti17 titanium alloy; microstructure; mechanical properties; deformation behavior