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Welding-Induced Heterogeneity Promotes Gradient Nanostructuring in Laser-Welded 304 Stainless Steel Joints
Tianzhang Zhao1, Junping Zhu1,2, Hongchuan Deng3
1College of Aerospace Engineering, Shenyang Aerospace University, Shenyang 110136, China.
Nanomaterials (Basel, Switzerland)
|July 27, 2026
Summary
Surface mechanical rolling treatment (SMRT) enhances laser-welded stainless steel by refining microstructure and increasing strength. This method shifts fracture location from the weld metal to the base metal, improving joint reliability.
Area of Science:
- Materials Science
- Mechanical Engineering
- Metallurgy
Background:
- Laser-welded stainless steel joints exhibit microstructural heterogeneity, leading to strain localization and premature failure in the weld metal (WM).
- Key heterogeneities include Ni compositional fluctuations, oxide particles, and varied grain structures within the WM.
Purpose of the Study:
- To investigate the effectiveness of Surface Mechanical Rolling Treatment (SMRT) in enhancing the mechanical properties of laser-welded 304 stainless steel joints.
- To understand the role of microstructural features, particularly Ni concentration, in SMRT-induced property improvements.
Main Methods:
- Application of Surface Mechanical Rolling Treatment (SMRT) to laser-welded 304 stainless steel plates.
- Microstructural characterization (e.g., grain structure, nanostructure, composition) and hardness testing of the weld metal (WM) and base metal (BM).
- Uniaxial tensile testing to evaluate yield strength, ultimate tensile strength, and elongation, and to determine fracture location.
Main Results:
- SMRT induced significant grain refinement and gradient nanostructures in the WM, surpassing those in the base metal (BM).
- Near-surface hardness of the WM increased to ~500 Hv, substantially higher than the BM.
- Tensile tests showed a dramatic increase in yield strength (~350 MPa to ~700 MPa) and ultimate tensile strength (~1000 MPa with ~40% elongation).
- Fracture location shifted from the WM to the BM post-SMRT.
Conclusions:
- SMRT effectively enhances the mechanical performance of laser-welded stainless steel by promoting martensitic transformation and creating gradient nanostructures.
- The improved microstructure suppresses strain localization, leading to a significant increase in strength and elongation.
- SMRT enhances the mechanical reliability of welded joints, shifting failure away from the critical weld metal region.
