Correlation of local strain with microstructures around fusion zone of a Cr-Ni-Mo-V steel welded joint

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• 作者：De-Qiang Wang ; Ming-Liang Zhu ; ^{mlzhu@ecust.edu.cn} ; Fu-Zhen Xuan ; ^{fzxuan@ecust.edu.cn}
• 关键词：Strain measurement ; Digital image correlation ; Welded joint ; Local strain
• 刊名：Materials Science and Engineering: A
• 出版年：2017
• 出版时间：8 February 2017
• 年：2017
• 卷：685
• 期：Complete
• 页码：205-212
• 全文大小：1488 K
• 卷排序：685

文摘

In this paper, in-situ SEM images with both low and high resolution near fusion line of a Cr-Ni-Mo-V steel welded joint were taken during interrupted monotonic tensile tests, with which macro- and micro-strain were measured based on digital image correlation technique and correlated with microstructures. An error analysis of strain measurement indicated sufficient resolution for image correlation with intrinsic microstructures as speckles. Results from digital image correlation showed that base metal, heat-affected zone and weld metal of the welds exhibited different responses to external tensile loading with mismatched strain distribution. A transfer of strain localisation from tempered martensites at base metal to lathy bainites at weld metal was observed around the fusion zone, due to varied hardening capabilities among non-homogeneous microstructures. Micro-strain could be several times higher than macro-strain at the same strained area, implying severe non-uniform deformation at microstructural scale. The most straining zone around the fusion line was found to be localized at blocks of soft δ-ferrites.