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<p>Directed Energy Deposition (DED) is a widely utilized additive manufacturing technology in high-performance industries, but post-processing such as machining is often required to improve surface quality and dimensional accuracy. This study investigates the effects of microstructural evolution during DED additive manufacturing on the post-machining behavior of Ti-6Al-4&#xa0;V alloy. Specimens were fabricated under varying laser power (200–440&#xa0;W) and powder feed rates (0.5–1.0&#xa0;g/min), followed by slot milling. High laser power (e.g., 440&#xa0;W) induced rapid melting and solidification, forming a finer grain structure and significantly increasing surface hardness (up to 414.3 HV). In contrast, excessive powder feed led to incomplete fusion, resulting in porosity and reduced hardness. During post-machining, cutting force and surface roughness significantly depended on laser power and machining parameters. Under high laser power and aggressive machining conditions, cutting force and surface roughness increased by up to 73.26% and 20.48%, respectively, compared to annealed Ti-6Al-4&#xa0;V. Machined surface hardness also increased with high cutting speed and feed rate due to strain hardening and compressive stress development, especially in high-strength DED materials. Considering the observed microstructure-dependent machinability degradation, it is concluded that a laser power of ≤ 320&#xa0;W at 0.5&#xa0;g/min constitutes the design-safe DED parameter window for Ti-6Al-4&#xa0;V components intended for subsequent machining operations, with the 440&#xa0;W condition identified as exceeding the empirical machinability threshold within the tested parameter space.</p>

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Effect of Microstructural Properties on the Post-machining Behavior of DED Additive Manufactured Ti-6Al-4V Alloy

  • 期刊论文

  • 发表日期：

    2026年7月24日

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  • Min Gi Ha,
  • Hyunmin Park,
  • Hyung Wook Park,
  • Martin Byung-Guk Jun,
  • Do Young Kim,
  • Joo Sung Yoon

摘要

Directed Energy Deposition (DED) is a widely utilized additive manufacturing technology in high-performance industries, but post-processing such as machining is often required to improve surface quality and dimensional accuracy. This study investigates the effects of microstructural evolution during DED additive manufacturing on the post-machining behavior of Ti-6Al-4 V alloy. Specimens were fabricated under varying laser power (200–440 W) and powder feed rates (0.5–1.0 g/min), followed by slot milling. High laser power (e.g., 440 W) induced rapid melting and solidification, forming a finer grain structure and significantly increasing surface hardness (up to 414.3 HV). In contrast, excessive powder feed led to incomplete fusion, resulting in porosity and reduced hardness. During post-machining, cutting force and surface roughness significantly depended on laser power and machining parameters. Under high laser power and aggressive machining conditions, cutting force and surface roughness increased by up to 73.26% and 20.48%, respectively, compared to annealed Ti-6Al-4 V. Machined surface hardness also increased with high cutting speed and feed rate due to strain hardening and compressive stress development, especially in high-strength DED materials. Considering the observed microstructure-dependent machinability degradation, it is concluded that a laser power of ≤ 320 W at 0.5 g/min constitutes the design-safe DED parameter window for Ti-6Al-4 V components intended for subsequent machining operations, with the 440 W condition identified as exceeding the empirical machinability threshold within the tested parameter space.