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

Abstract

WAAM (Wire Arc Additive Manufacturing) has been widely used due to its advantages of high processing freedom, low cost and high efficiency. However, one of the most relevant unsolved problems in WAAM is the heat accumulation caused by high heat input. In this study, the compressed argon‐based interlayer AC (Active Cooling) process is employed to reduce heat accumulation, and the influence mechanism on microstructure and mechanical properties of Ti‐6Al‐4V samples were revealed. The results show that the introduction of interlayer AC leads to the interlayer temperature decreases from 468 °C to 53 °C, and the widths of prior‐β columnar grains and αGB are refined. The increase of cooling rate (380 °C/s → 604 °C/s) results in the transformation of large‐sized colonies into finer basketweave structure, accompanied by the production of martensite α’ and a slight increase of β phase content. The finer basketweave structure increase the strength of the samples, while the narrower αGB 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 of the AC samples 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.This article is protected by copyright. All rights reserved.