Temperature Dependence of Tensile Properties and Fracture Behavior of Welded Joints of Titanium Matrix Composites in Gas Tungsten Arc Welding

摘要

The characteristics of gas tungsten arc weldments of in-situ reinforced titanium matrix composites were investigated, and the joint quality was evaluated by means of weld morphology, microstracture and tensile tests. With an increase of welding process parameters, sound welded joints were fabricated. The weld zone had a refinement microstructure and TiB_w exhibited smaller sizes and dispersed distribution, forming a novel network structure in the weld. Tensile tests indicated that the weld presented excellent high temperature strengths, even superior to the base metal under the welding conditions. The welded joints displayed a slower downtrend in strength than that of base metal with an increase of temperature, and the elongation values of joints were higher than the base metal because of the refined grain microstructure and dispersed distribution of TiB_w in the weld. The strengthening mechanism of high temperature properties of welded joints is ascribed to smaller sizes and network structure of TiB_w in the weld. The fracture surfaces of butt joints for TMCs include the hybrid ductile of matrix and brittle fracture/ decohesion of TiB_w at different temperatures.