Defect features, texture and mechanical properties of friction stir welded lap joints of 2A97 Al-Li alloy thin sheets

Journal Article · Wed Mar 15 04:00:00 EDT 2017 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2017.01.038· OSTI ID:22689731

Chen, Haiyan ^[1]; Fu, Li ^[1]; Liang, Pei; Liu, Fenjun ^[2]

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1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072 (China)
2. Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi'an 710072 (China)

1.4 mm 2A97 Al-Li alloy thin sheets were welded by friction stir lap welding using the stirring tools with different pin length at different rotational speeds. The influence of pin length and rotational speed on the defect features and mechanical properties of lap joints were investigated in detail. Microstructure observation shows that the hook defect geometry and size mainly varies with the pin length instead of the rotational speed. The size of hook defects on both the advancing side (AS) and the retreating side (RS) increased with increasing the pin length, leading to the effective sheet thickness decreased accordingly. Electron backscatter diffraction analysis reveals that the weld zones, especially the nugget zone (NZ), have the much lower texture intensity than the base metal. Some new texture components are formed in the thermo-mechanical affected zone (TMAZ) and the NZ of joint. Lap shear test results show that the failure load of joints generally decreases with increasing the pin length and the rotational speed. The joints failed during the lap shear tests at three locations: the lap interface, the RS of the top sheet and the AS of the bottom sheet. The fracture locations are mainly determined by the hook defects. - Highlights: • Hook defect size mainly varies with the pin length of stirring tool. • The proportion of LAGBs and substructured grains increases from NZ to TMAZ. • Weld zones, especially the NZ, have the much lower texture intensity than the BM. • Lap shear failure load and fracture location of joints is relative to the hook defects.

• OSTI ID: 22689731
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 125; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
BACKSCATTERING
DEFECTS
ELECTRON DIFFRACTION
FRACTURES
FRICTION
HEAT AFFECTED ZONE
LENGTH
LITHIUM ALLOYS
MECHANICAL PROPERTIES
MICROSTRUCTURE
SHEETS
TEXTURE
THICKNESS
VELOCITY
WELDED JOINTS
WELDING