Friction stir welding of 2195 AlLi alloy: Effect of microstructure on joint failure

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

Materials Characterization Pub Date : 2025-04-23 DOI:10.1016/j.matchar.2025.115077

Yaxing Tong , Bolun Dong , Xiaoyu Cai , Hua Zhang , Sanbao Lin

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Abstract

This study presents a comprehensive analysis of the failure mechanisms in friction stir welded (FSW) joints of 2195 aluminum‑lithium alloy, aiming to uncover the microstructural evolution, texture changes, precipitate phase behavior, and their impact on mechanical properties in regions near failure locations. FSW of 2195 AlLi alloy was performed at room temperature with welding parameters of 425 rpm rotational speed and 100 mm/min welding speed. The analysis, combining tensile testing and digital image correlation (DIC) techniques, revealed that local strain migrated from the heat-affected zone (HAZ) on the retreating side towards the HAZ on the advancing side, with fracture ultimately occurring at the interface between the HAZ and the thermo-mechanically affected zone on the advancing side (TMAZ-AS). A systematic investigation of the microstructural evolution in the fracture region was conducted using transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), differential scanning calorimetry (DSC), microhardness testing, and finite element modeling (FEM). The results indicated an increase in deformation texture strength in the HAZ, while the TMAZ-AS exhibited shear texture. The HAZ showed lower average kernel average misorientation values and dislocation density, indicating less localized plastic deformation in this region. The decrease in microhardness from the base material (BM) to the HAZ was attributed to the coarsening of T₁ and δ’/β’ phases, while the increase in hardness from the HAZ to the TMAZ-AS was due to solid solution and dislocation strengthening. FEM simulations demonstrated that the HAZ experienced temperatures between 220 and 300 °C, while the TMAZ-AS reached 300–500 °C. Micro-cracks were observed along grain boundary precipitates in the HAZ, and the presence of a wide precipitate-free zone (PFZ) was identified as the primary cause of tensile fracture, which exhibited a quasi-cleavage fracture mechanism.

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2195 AlLi合金搅拌摩擦焊：显微组织对接头失效的影响

本文对2195铝锂合金搅拌摩擦焊接接头的失效机理进行了全面分析，旨在揭示失效点附近区域的组织演变、织构变化、析出相行为及其对力学性能的影响。在425 rpm转速和100 mm/min焊接速度条件下，对2195 AlLi合金进行了室温搅拌焊。结合拉伸测试和数字图像相关（DIC）技术的分析表明，局部应变从后退侧热影响区（HAZ）向前进侧热影响区（HAZ）迁移，最终在HAZ与前进侧热机械影响区（TMAZ-AS）之间的界面发生断裂。采用透射电子显微镜（TEM）、电子背散射衍射（EBSD）、x射线衍射（XRD）、差示扫描量热法（DSC）、显微硬度测试和有限元建模（FEM）对断口区域的微观组织演变进行了系统的研究。结果表明，热影响区变形织构强度增加，而TMAZ-AS呈现剪切织构。热影响区平均核位错值和位错密度较低，表明该区域局部塑性变形较小。从基材（BM）到HAZ的显微硬度下降是由于T1和δ′/β′相的粗化，而从HAZ到TMAZ-AS的硬度增加是由于固溶体和位错强化。有限元模拟结果表明，热影响区温度为220 ~ 300℃，热影响区温度为300 ~ 500℃。热影响区沿晶界析出物观察到微裂纹，宽无析出区（PFZ）的存在是拉伸断裂的主要原因，表现为准解理断裂机制。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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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.