The metallurgical behaviors and crystallographic characteristic on macro deformation mechanism of 316 L laser-MIG hybrid welded joint

• Published in: Materials & design 2020-09, Vol.194, p.108893, Article 108893
• Main Authors: Zhu, Zhengwu, Ma, Xiuquan, Wang, Chunming, Mi, Gaoyang, Zheng, Shuye
• Format: Article
• Language: English
• Subjects: 316 L stainless steel; Deformation mechanism; Laser-MIG hybrid welding; Microstructure; Microtexture
• ISSN: 0264-1275
• DOI: 10.1016/j.matdes.2020.108893

A 10 mm 316 L stainless steel plate was joined using multi-layer laser-MIG hybrid welding. Results showed that unmixed zone and “real” fusion zone (FZ) existed near the fusion line. Frequently met dendritic ferrite (δ) and newly encountered spherical nanoscale particles trapped in austenite (γ) were only observed in the latter region. Chemically, these particles turned out a SiO2 phase. From base metal to FZ, δ morphology was altered from originally linear to relatively diversely dendritic. Meantime, γ exhibited a converse manner where previously randomly oriented equiaxed was replaced by coarse, columnar and textured. Accordingly, a comparably high Schmidt factor in γ phase was obtained in FZ. Moreover, δ exhibited a relatively higher stress level than γ which presented a decrease in residual stress with grain coarsening in heat affected zone. In FZ, δ fraction displayed a dramatical increase with special BCC-FCC orientation relations established. Finally, tensile test and fracture appearance implied that FZ was exactly the weakest link of the whole welded joint in spite of a qualified strength achieved. In summary, lack in Σ3, largely increased δ fraction, high Schmidt factor in γ and especially being rich in SiO2 particles collectively led to the micro-void coalescence fracture in FZ. [Display omitted] •Unmixed zone and “real” fusion zone were firstly clarified in 316 L laser-MIG hybrid weld.•The “real” fusion zone was full of dendritic ferrite and newly encountered spherical nanoscale SiO2 particles.•Microstructures and microtextures were systematically studied and compared concerning ferrite and austenite.•Lack in Σ3, increased δ fraction, high Schmidt factor and being trapped with SiO2 particles led to the micro-void coalescence fracture in fusion zone.