Towards an explanation of liquid metal embrittlement cracking in resistance spot welding of dissimilar steels

Zhanxiang Ling; Min Wang; Liang Kong; Ke Chen

Materials & Design (Oct 2020)

Towards an explanation of liquid metal embrittlement cracking in resistance spot welding of dissimilar steels

Zhanxiang Ling,
Min Wang,
Liang Kong,
Ke Chen

Affiliations

Zhanxiang Ling: Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, China
Min Wang: Corresponding authors at: Room 403, F building, School of Materials Science and Engineering, Shanghai Jiao Tong University, No.800 Dongchuan Road, Minhang District, Shanghai 200240, China.; Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, China
Liang Kong: Corresponding authors at: Room 403, F building, School of Materials Science and Engineering, Shanghai Jiao Tong University, No.800 Dongchuan Road, Minhang District, Shanghai 200240, China.; Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, China
Ke Chen: Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai Jiao Tong University, Shanghai 200240, China

Journal volume & issue: Vol. 195
p. 109055

Abstract

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Automotive advanced high-strength steels and ultra-high-strength steels, such as Q&P980 steel with a Zn coating, are prone to liquid metal embrittlement (LME) surface cracking during resistance spot welding, while traditional low carbon steels (LCSs) do not appear to undergo LME. In this work, galvanized Q&P980 steel sheets were welded with LCS sheets. LME cracks were found on both the Q&P980 steel and LCS sides. However, the severity of LME cracking on the Q&P980 side was much higher than that on the LCS side, indicating that Q&P980 steel has a higher LME susceptibility than LCS, which was also proven by a hot tensile test. The higher LME susceptibility of Q&P980 was attributed to its lower reactivity with liquid Zn, higher achievable stress and increased number of LME-susceptible grain boundaries. Micro-analysis revealed that Zn most likely entered the steel matrix via diffusion and not via liquid penetration, and stress-assisted diffusion is the likely mechanism for LME.

Published in Materials & Design

ISSN: 0264-1275 (Print); 1873-4197 (Online)
Publisher: Elsevier
Country of publisher: United Kingdom
LCC subjects: Technology: Electrical engineering. Electronics. Nuclear engineering: Materials of engineering and construction. Mechanics of materials
Website: https://www.journals.elsevier.com/materials-and-design

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