Study on δ-ferrite evolution and properties of laser fusion zone during post-weld heat treatment on Al-Si coated press-hardened steel

Xiaonan Wang; Ge Yi; Qian Sun; Ming Xiao; Yuan Gao; Zhenghui Zhang; Hongshuang Di; Y. Norman Zhou

Journal of Materials Research and Technology (May 2020)

Study on δ-ferrite evolution and properties of laser fusion zone during post-weld heat treatment on Al-Si coated press-hardened steel

Xiaonan Wang,
Ge Yi,
Qian Sun,
Ming Xiao,
Yuan Gao,
Zhenghui Zhang,
Hongshuang Di,
Y. Norman Zhou

Affiliations

Xiaonan Wang: Shagang School of Iron and Steel, Soochow University, Suzhou, Jiangsu, 215021, PR China; Centre for Advanced Materials Joining, Department of Mechanical & Mechatronics Engineering, University of Waterloo, 200 University AvenueWest, Waterloo, Ontario, N2L 3G1, Canada; Corresponding authors.
Ge Yi: Shagang School of Iron and Steel, Soochow University, Suzhou, Jiangsu, 215021, PR China
Qian Sun: Centre for Advanced Materials Joining, Department of Mechanical & Mechatronics Engineering, University of Waterloo, 200 University AvenueWest, Waterloo, Ontario, N2L 3G1, Canada; The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang, Liaoning, 110819, PR China
Ming Xiao: Centre for Advanced Materials Joining, Department of Mechanical & Mechatronics Engineering, University of Waterloo, 200 University AvenueWest, Waterloo, Ontario, N2L 3G1, Canada
Yuan Gao: The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang, Liaoning, 110819, PR China
Zhenghui Zhang: Shagang School of Iron and Steel, Soochow University, Suzhou, Jiangsu, 215021, PR China
Hongshuang Di: The State Key Laboratory of Rolling and Automation, Northeastern University, Shenyang, Liaoning, 110819, PR China; Corresponding authors.
Y. Norman Zhou: Centre for Advanced Materials Joining, Department of Mechanical & Mechatronics Engineering, University of Waterloo, 200 University AvenueWest, Waterloo, Ontario, N2L 3G1, Canada

Journal volume & issue: Vol. 9, no. 3
pp. 5712 – 5722

Abstract

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Laser welding of Al-Si coated press-hardened steel (PHS) was still a challenging due to the formation of δ-ferrite in the fusion zone. However, it was ambiguous on the δ-ferrite evolution during post-weld heat treatment (PWHT). In this study, Al-Si coated PHS was welded by laser fiber and then heat-treated at various temperatures (650 °C, 950 °C and 1050 °C), and the microstructure evolution was investigated by in situ-observation. Mechanical properties and formability of welded joints was analyzed. The results showed that δ-ferrite did not go through phase transformation during PWHT regardless of any temperature, but with a grain boundary flatted and movement. The presence of coarse δ-ferrite after PWHT was the responsible for the decreasing of tensile strength and formability of welded joints. The initiation crack was easy to generate in the phase interface between δ-ferrite and martensite to form a local brittle fracture zone finally. This study results provides a new theoretical criterion for the properties improvement on the laser welding of PHS without removing Al-Si coating.

Published in Journal of Materials Research and Technology

ISSN: 2238-7854 (Print); 2214-0697 (Online)
Publisher: Elsevier
Country of publisher: Netherlands
LCC subjects: Technology: Mining engineering. Metallurgy
Website: https://www.journals.elsevier.com/journal-of-materials-research-and-technology/

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