Effect of Interlayer-Compressed Argon Gas Active Cooling on Microstructure and Properties of Ti-6Al-4V Fabricated by WAAM

Wire arc additive manufacturing (WAAM) has been widely used due to its advantages of low cost and high efficiency. However, one of the unsolved problems in WAAM is the heat accumulation. In this study, the compressed argon-based interlayer active cooling (AC) process is employed to reduce heat accumulation, and the influence mechanism on microstructure and mechanical properties of Ti-6Al-4V samples are revealed. It is shown in the results that the introduction of interlayer AC leads to the interlayer temperature decreases from 468 to 53 & DEG;C, and the widths of prior-& beta; grains and & alpha;(GB) are refined. The increase of cooling rate (380-604 & DEG;C s(-1)) results in the transformation of large-sized colonies into finer basket weave structure, accompanied by the production of martensite & alpha;'. The finer basket weave structure increases the strength of the samples, while the narrower & alpha;(GB) and the high-angle grain boundaries increase the resistance of crack propagation. The high dislocation density caused by the faster cooling rate increases the plastic deformation to a certain extent. As a result, the interlayer AC improves the strength and plasticity of the samples simultaneously, the samples change from brittle and ductile-mixed fracture to ductile fracture mode.