Microstructural Evolution, Deformation Mechanisms and Texture Development in Friction Stir Welded Nickel and Molybdenum Free-High Nitrogen Austenitic Stainless Steel

IF 4.8 2区材料科学 Q1 MATERIALS SCIENCE, CHARACTERIZATION & TESTING

Materials Characterization Pub Date : 2025-05-06 DOI:10.1016/j.matchar.2025.115129

Arun Kumar Gurrala, Raffi Mohammed

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Abstract

This study presents a comprehensive analysis of the microstructural evolution, deformation mechanisms, and textural development in friction stir-welded (FSW) novel nickel- and molybdenum-free high nitrogen austenitic stainless steel (HNASS) through electron backscatter diffraction (EBSD) techniques. We delineate the distinct microstructural transformations occurring on the advancing side (AS) and retreating side (RS) within the stir zone (SZ), thermo-mechanically affected zone (TMAZ), and heat-affected zone (HAZ). The base metal (BM) is characterized by an equiaxed austenitic grain structure, enriched with a high density of high-angle grain boundaries (HAGBs) and coincidence site lattice (CSL) boundaries, reflective of its well-annealed state. The FSW process engendered significantly higher strain rates and thermal gradients on the AS relative to the RS, leading to refined grain structures and an intensified dynamic recrystallization (DRX) process. Notably, discontinuous dynamic recrystallization (DDRX) was identified as a predominant grain refinement mechanism, exerting a more substantial influence on the AS due to elevated strain and temperature conditions. In-depth analysis of grain boundary character distribution (GBCD), kernel average misorientation (KAM), grain orientation spread (GOS), and grain average misorientation (GAM) across the different weld zones revealed pronounced plastic deformation and internal strain on the AS. Furthermore, textural analysis uncovered key shear components in the SZ, imparting distinct microstructural and textural attributes. This investigation sheds light on the intricate interactions between deformation, recrystallization, shear, and thermal effects during FSW, offering new insights into the mechanisms that enhance the mechanical properties and corrosion resistance of welded joints in nickel and molybdenum-free HNASS. The findings provide a critical foundation for optimizing FSW parameters to achieve superior material performance.

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无镍、无钼高氮奥氏体不锈钢搅拌摩擦焊接的组织演变、变形机制和织构发展

利用电子背散射衍射（EBSD）技术，对新型无镍无钼高氮奥氏体不锈钢（HNASS）摩擦搅拌焊（FSW）的显微组织演变、变形机制和织构发展进行了全面分析。我们描述了在搅拌区（SZ）、热机械影响区（TMAZ）和热影响区（HAZ）中，在前进侧（AS）和后退侧（RS）发生的不同的显微组织转变。母材（BM）具有等轴奥氏体晶粒结构，富含高密度的高角晶界（HAGBs）和重合点阵（CSL）晶界，反映了其良好的退火状态。相对于RS， FSW过程在AS上产生了更高的应变速率和热梯度，导致晶粒结构细化和动态再结晶（DRX）过程加剧。值得注意的是，不连续动态再结晶（DDRX）被确定为主要的晶粒细化机制，由于应变和温度的升高，对as产生了更大的影响。对不同焊缝区的晶界特征分布（GBCD）、核平均取向偏差（KAM）、晶粒取向扩展（GOS）和晶粒平均取向偏差（GAM）进行深入分析，发现AS存在明显的塑性变形和内部应变。此外，结构分析揭示了SZ的关键剪切成分，赋予其独特的微观结构和结构属性。这项研究揭示了FSW过程中变形、再结晶、剪切和热效应之间复杂的相互作用，为提高无镍和无钼HNASS焊接接头的力学性能和耐腐蚀性的机制提供了新的见解。研究结果为优化FSW参数以获得优异的材料性能提供了关键基础。

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来源期刊

Materials Characterization 工程技术-材料科学：表征与测试

CiteScore

7.60

自引率

8.50%

发文量

746

审稿时长

36 days

期刊介绍： Materials Characterization features original articles and state-of-the-art reviews on theoretical and practical aspects of the structure and behaviour of materials. The Journal focuses on all characterization techniques, including all forms of microscopy (light, electron, acoustic, etc.,) and analysis (especially microanalysis and surface analytical techniques). Developments in both this wide range of techniques and their application to the quantification of the microstructure of materials are essential facets of the Journal. The Journal provides the Materials Scientist/Engineer with up-to-date information on many types of materials with an underlying theme of explaining the behavior of materials using novel approaches. Materials covered by the journal include: Metals & Alloys Ceramics Nanomaterials Biomedical materials Optical materials Composites Natural Materials.