Microstructural refinement mechanism and its effect on toughness in the nugget zone of high-strength pipeline steel by friction stir welding. (10th December 2021)

• Record Type: Journal Article
• Authors: Duan, R.H.; Xie, G.M.; Xue, P.; Ma, Z.Y.; Luo, Z.A.; Wang, C.; Misra, R.D.K.; Wang, G.D.
• Is Part Of: Journal of materials science & technology. Volume 93(2022)
• Page Start: 221
• Page End: 231
• Publication Date: 2021-12-10
• Subjects: Pipeline steel -- Friction stir welding -- Grain refinement -- M-A constituent -- Toughness; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2021.04.008
• Languages: English
• ISSNs: 1005-0302

Abstract

Highlights: The thermo-mechanical process during FSW pipeline steel in the NZ was simulated by multi-pass thermal compression. The influence of the dynamic recrystallization (DRX) process was studied during thermal deformation. The austenitic non-DRX caused a significant grain refinement and an improvement in toughness simultaneously. Abstract: High-strength pipeline steel was subjected to friction stir welding (FSW) at rotation rates of 400–700 rpm, and the grain refinement mechanism of the nugget zone (NZ) was determined. The thermo-mechanical process during FSW in the NZ was simulated by multi-pass thermal compression, thereby achieving the austenitic non-recrystallization temperature ( T nr ). The austenitic non-recrystallization in the NZ at the lowest rotation rate of 400 rpm caused a significant grain refinement. Furthermore, the reduced rotation rate also resulted in the formation of a high ratio of island-like martensite-austenite (M-A) constituent. The toughness of the NZs was enhanced as the rotation rate decreased, which is attributed to the fine effective grains and homogeneously distributed fine M-A constituents dramatically inhibiting crack initiation and propagation. Graphical abstract: Image, graphical abstract