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<p>Due to the formation of brittle martensite, cracks easily form in the high strength–ductility high-carbon (C) quenching–partitioning–tempering (Q–P–T) steel-welded joint, which degrades mechanical properties and limits the application of the high-C Q–P–T steel. In the present study, a high-C Q–P–T steel was laser welded and treated by partitioning-aging process. The microstructure variation, mechanical properties, and failure mechanism of the laser-welded joint were systematically investigated. In the as-welded joint, due to high-C regions within the liquid molten core and heat-affected zone (HAZ), micro-cracks exist in the fusion zone (FZ) and HAZ, which consist twin martensite and lead to brittle fracture. During partitioning-aging process, formation of cementite is suppressed by Si and micro-cracks in FZ and HAZ are fixed by transition carbides. Besides, C partitions from martensite to newly formed reverted austenite during partitioning aging, which enhances the deformability of martensite and stabilizes reverted austenite. The C-enriched reverted austenite in the partitioning-aging processed joint generates dislocation across martensite/austenite interface (DAMAI) effect and transformation-induced plasticity (TRIP) effect under deformation, which enables the high-C Q–P–T steel joint with extraordinary strength–ductility. The partitioning-aging process promotes the industrial application of high-C Q–P–T steel and provides new route for designing and welding of ultra-high-strength steels.</p>

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Effect of Partitioning-Aging Process on Microstructure and Mechanical Properties of Laser-Welded High-Carbon Quenching–Partitioning–Tempering Steel Joint

  • 期刊论文

  • 发表日期：

    2026年3月4日

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  • Jiazhi Zhang,
  • Yufei Han,
  • Xuzhi Zhang,
  • Jiazhuang Tian,
  • Zhengqiang Zhu,
  • Shanglu Yang

摘要

Due to the formation of brittle martensite, cracks easily form in the high strength–ductility high-carbon (C) quenching–partitioning–tempering (Q–P–T) steel-welded joint, which degrades mechanical properties and limits the application of the high-C Q–P–T steel. In the present study, a high-C Q–P–T steel was laser welded and treated by partitioning-aging process. The microstructure variation, mechanical properties, and failure mechanism of the laser-welded joint were systematically investigated. In the as-welded joint, due to high-C regions within the liquid molten core and heat-affected zone (HAZ), micro-cracks exist in the fusion zone (FZ) and HAZ, which consist twin martensite and lead to brittle fracture. During partitioning-aging process, formation of cementite is suppressed by Si and micro-cracks in FZ and HAZ are fixed by transition carbides. Besides, C partitions from martensite to newly formed reverted austenite during partitioning aging, which enhances the deformability of martensite and stabilizes reverted austenite. The C-enriched reverted austenite in the partitioning-aging processed joint generates dislocation across martensite/austenite interface (DAMAI) effect and transformation-induced plasticity (TRIP) effect under deformation, which enables the high-C Q–P–T steel joint with extraordinary strength–ductility. The partitioning-aging process promotes the industrial application of high-C Q–P–T steel and provides new route for designing and welding of ultra-high-strength steels.