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<p>This study investigated the microstructure and mechanical properties of ultra-high-strength steel (UHSS) fabricated by cored wire arc additive manufacturing (WAAM) under various heat treatment conditions. Multi-step heat treatments consisting of partitioning at 630–690&#xa0;°C followed by tempering at 550&#xa0;°C were employed to optimize material performance. Results indicate that reversed austenite (RA) content exhibited a non-monotonic response to partitioning temperature, reaching a maximum of 11.98 ± 0.93% at 670&#xa0;°C. At this optimal condition, RA formed a Kurdjumov–Sachs (K–S) orientation relationship with martensite, substantially enhancing transformation-induced ductility (TRIP) effects and yielding superior strength-ductility synergy (tensile strength: 1167 ± 5&#xa0;MPa; elongation: 19.3 ± 0.2%; impact energy: 45 ± 2.6 J). Conversely, 650&#xa0;°C-treated steels displayed reduced impact toughness (31 ± 2.1 J) attributable to high interfacial stresses from coarse martensite formation. The treatment at 690&#xa0;°C resulted in an increase in yield strength to 980 ± 17&#xa0;MPa, attributed to a higher volume fraction of LM; however, this enhancement was accompanied by a reduction in ductility, which correlated with a decrease in RA (8.85%). These findings elucidate microstructure–property relationships in WAAM-processed UHSS and establish effective thermal processing strategies for balanced mechanical performance.</p>

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Microstructural evolution and enhanced mechanical performance in cored-wire arc additive manufactured ultra-high strength steel by multi-step heat treatment

  • 期刊论文

  • 发表日期：

    2025年10月30日

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  • Shun Li,
  • Yuezhang Ju,
  • Xiaocong Yang,
  • Chengning Li,
  • Xinjie Di

摘要

This study investigated the microstructure and mechanical properties of ultra-high-strength steel (UHSS) fabricated by cored wire arc additive manufacturing (WAAM) under various heat treatment conditions. Multi-step heat treatments consisting of partitioning at 630–690 °C followed by tempering at 550 °C were employed to optimize material performance. Results indicate that reversed austenite (RA) content exhibited a non-monotonic response to partitioning temperature, reaching a maximum of 11.98 ± 0.93% at 670 °C. At this optimal condition, RA formed a Kurdjumov–Sachs (K–S) orientation relationship with martensite, substantially enhancing transformation-induced ductility (TRIP) effects and yielding superior strength-ductility synergy (tensile strength: 1167 ± 5 MPa; elongation: 19.3 ± 0.2%; impact energy: 45 ± 2.6 J). Conversely, 650 °C-treated steels displayed reduced impact toughness (31 ± 2.1 J) attributable to high interfacial stresses from coarse martensite formation. The treatment at 690 °C resulted in an increase in yield strength to 980 ± 17 MPa, attributed to a higher volume fraction of LM; however, this enhancement was accompanied by a reduction in ductility, which correlated with a decrease in RA (8.85%). These findings elucidate microstructure–property relationships in WAAM-processed UHSS and establish effective thermal processing strategies for balanced mechanical performance.