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<p>This study presents a comprehensive in-situ analysis of the microstructural characteristics and mechanical behavior of laser-based directed energy deposition (LB-DED)-repaired H13 tool steel, with a focus on the heterogeneous interfacial transition zone. By integrating in-situ scanning electron microscopy tensile testing and digital image correlation strain mapping, we elucidate the deformation mechanisms and crack initiation behavior across distinct microstructural zones, including the deposited zone (DZ), remelted zone (RZ), heat-affected zone (HAZ), and substrate (SUB). The four zones exhibit significant variations in dislocation density, grain morphology and size as well as carbide distribution. Strain localizes preferentially at the HAZ/SUB interface due to its lower geometrically necessary dislocation density, which promotes earlier dislocation activation and pile-up, leading to higher microcrack density and final fracture along this interface. The results demonstrate that microstructural differences govern damage initiation and propagation, suggesting that precise energy input control can optimize HAZ characteristics to enhance interfacial strength. This work provides critical insights for improving LB-DED repair strategies in tool steels by linking microstructural heterogeneity to failure mechanisms.</p> Graphical Abstract <p></p>

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In-Situ Investigation of Microstructure-Dependent Deformation and Fracture at the Heterogeneous Interface of Laser-Based Direct Energy Deposited and Tempered H13 Steel

  • 期刊论文

  • 发表日期：

    2025年11月7日

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  • Guo Wang,
  • Haidong Zhao,
  • Chaoyang Deng,
  • Wenyou Ma

摘要

This study presents a comprehensive in-situ analysis of the microstructural characteristics and mechanical behavior of laser-based directed energy deposition (LB-DED)-repaired H13 tool steel, with a focus on the heterogeneous interfacial transition zone. By integrating in-situ scanning electron microscopy tensile testing and digital image correlation strain mapping, we elucidate the deformation mechanisms and crack initiation behavior across distinct microstructural zones, including the deposited zone (DZ), remelted zone (RZ), heat-affected zone (HAZ), and substrate (SUB). The four zones exhibit significant variations in dislocation density, grain morphology and size as well as carbide distribution. Strain localizes preferentially at the HAZ/SUB interface due to its lower geometrically necessary dislocation density, which promotes earlier dislocation activation and pile-up, leading to higher microcrack density and final fracture along this interface. The results demonstrate that microstructural differences govern damage initiation and propagation, suggesting that precise energy input control can optimize HAZ characteristics to enhance interfacial strength. This work provides critical insights for improving LB-DED repair strategies in tool steels by linking microstructural heterogeneity to failure mechanisms.

Graphical Abstract