Fine equiaxed zone induced softening and failure behavior of 7050 aluminum alloy hybrid laser welds

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:821

Article

Hu, Yanan¹  Wu, Shengchuan¹  Shen, Zhao²  Cao, Huatang³  Zhong, Xiangli³  Withers, Philip J.³ 

[1] Southwest Jiaotong Univ, State Key Lab Tract Power, Chengdu 610031, Peoples R China

[2] Univ Oxford, Dept Mat, Pk Rd, Oxford OX1 3PH, England

[3] Univ Manchester, Henry Royce Inst, Dept Mat, Manchester M13 9PL, Lancs, England

关键词: Laser welded aluminum alloy;    Non-dendritic equiaxed grain zone;    Nanoindentation;    Synchrotron X-ray tomography;    Intergranular cracking;   

DOI  :  10.1016/j.msea.2021.141597

来源: Elsevier

【 摘 要 】

A fine (similar to 3-10 mu m) equiaxed zone (FQZ) between the heat affected zone and the weld metal is a unique microstructural feature associated with fusion welded Zr-containing aluminum alloys, posing a significant threat to the structural integrity of welded components. This work examines the softening and failure behavior of a 7050-T7451 hybrid laser welded joint. Nanoindentation test results show the FQZ to have the lowest hardness across the welded joint, which is attributed primarily to a significant reduction in strengthening precipitates within the grains. The high-angle grain boundaries in the FQZ are decorated with an interconnected network of coarse brittle omega (Al7Cu2Fe) and S (Al2CuMg) phases. The damage sequence recorded by time-lapse X-ray computed tomography (CT) and in situ scanning electron microscopy (SEM) shows that these phases give rise to intergranular failure through the FQZ by void nucleation and link-up at low overall levels of plasticity, aided by the plastic incompatibility with these phases and the strain localisation.

【 授权许可】

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