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In this study, active interpass cooling using various compressed CO2 gas strategies was applied to wire-arc additively manufactured Ti–6Al–4V alloy, and as-manufactured microstructure characteristics, including phase composition, grain growth and microhardness, were fully explored by using Electron Backscattered Diffraction and hardness tester. Results show that rapid interpass cooling brings obvious martensite phase transformation, primarily from lamellar α grains to acicular α grains, to the deposited component. The microstructure tends to be fine-grained, disordered and displays reduced texture strength and increased dislocation density through visible coloration. This feature also exhibits high hardness values that brings an improvement in mechanical strength to deposited metal. Moreover, it is found cooling time variation could obtain better grain refinement than altering cooling gas flow rate during deposit, which is probably related to effective heat dissipation. The research findings can provide significant insight into microstructural evolution mechanism in wire-arc directed energy deposition process, and benefits to properties control.

The ability to control phases in eutectic high-entropy alloys (EHEAs) remains a formidable challenge. This study illustrates a simple approach that applies various sintering temperature and pressure to achieve precise control of phase transformation in AlCoCrFeNi2.1 EHEA, particularly to further enhance its corrosion resistance. The result display that at high sintering pressure, pore density in sintered material could be reduced significantly, and at high sintering temperature, BCC phase is seen a notable growth, which both determine the corrosion performance of studied alloy. Moreover, it is found that large BCC phase size could reduce micro-galvanic effect between FCC and BCC and then improve corrosion resistance. This work may provide a technological implication in the EHEA design for anti-corrosion.