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<p>This study employed two ultra-low-carbon welding wires with distinct carbon contents (0.050 wt.% and 0.019 wt.%) for gas metal arc welding experiments. The deposited metals WM1 and WM2 were systematically characterized using XRD, OM, SEM, EBSD, TEM, and ODF techniques to analyze grain orientation, grain boundary characteristics, dislocation density, substructure formation, and low-temperature toughness. Experimental results demonstrate that reducing carbon content from 0.054 to 0.026% induces significant microstructural transformations. The primary constituents shift from lath bainite and acicular ferrite to proeutectoid ferrite and side-plate ferrite, accompanied by a 40.23% increase in average grain size and 90.39% enhancement in texture intensity. Concurrently, intragranular dislocation density decreases by 67.24%. These microstructural modifications lead to a 12.74% reduction in tensile strength (from 926 to 808&#xa0;MPa) and a dramatic 77.42% decline in impact energy absorption at − 60&#xa0;°C (from 62 to 14&#xa0;J). Mechanistic analysis indicates carbon depletion alters crystallographic orientation, inducing grain boundary sliding transition. The compromised grain boundary compatibility critically impairs coordinated deformation capacity, while texture strengthening partially offsets strength loss at the expense of enhanced cleavage susceptibility.</p> Graphical abstract <p></p>

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Grain orientation changes and low-temperature brittle toughness transition caused by carbon element differences in the deposited metal

  • 期刊论文

  • 发表日期：

    2025年8月1日

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  • Tongbang An,
  • Liyin Zheng,
  • Zhihua Wang,
  • Chengyong Ma,
  • Yue Zuo,
  • Zhilong Cao

摘要

This study employed two ultra-low-carbon welding wires with distinct carbon contents (0.050 wt.% and 0.019 wt.%) for gas metal arc welding experiments. The deposited metals WM1 and WM2 were systematically characterized using XRD, OM, SEM, EBSD, TEM, and ODF techniques to analyze grain orientation, grain boundary characteristics, dislocation density, substructure formation, and low-temperature toughness. Experimental results demonstrate that reducing carbon content from 0.054 to 0.026% induces significant microstructural transformations. The primary constituents shift from lath bainite and acicular ferrite to proeutectoid ferrite and side-plate ferrite, accompanied by a 40.23% increase in average grain size and 90.39% enhancement in texture intensity. Concurrently, intragranular dislocation density decreases by 67.24%. These microstructural modifications lead to a 12.74% reduction in tensile strength (from 926 to 808 MPa) and a dramatic 77.42% decline in impact energy absorption at − 60 °C (from 62 to 14 J). Mechanistic analysis indicates carbon depletion alters crystallographic orientation, inducing grain boundary sliding transition. The compromised grain boundary compatibility critically impairs coordinated deformation capacity, while texture strengthening partially offsets strength loss at the expense of enhanced cleavage susceptibility.

Graphical abstract