Journal of Jilin University(Engineering and Technology Edition) ›› 2020, Vol. 50 ›› Issue (2): 512-519.doi: 10.13229/j.cnki.jdxbgxb20190241

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Microstructure and properties of 6082 aluminum alloyultra⁃thick plate preparated by friction stir weld

Wen-biao GONG1(),Rui ZHU1,Xin-zhe QIE1,Heng CUI2,Ming-yue GONG2   

  1. 1.Key Laboratory of Advanced Structural Materials, Ministry of Education, Changchun University of Technology, Changchun 130012, China
    2.Changchun Railway Vehicles Co. Ltd. , Changchun 130062, China
  • Received:2019-03-14 Online:2020-03-01 Published:2020-03-08

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Abstract:

The double-sided of friction stir butt welding was carried out on the 6082-T4 aluminum alloys with thickness of 84 mm , and artificial aging (180 ℃×5 h) was applied after welding. The microstructure and mechanical properties of welded joints along the thickness direction were studied. The results indicate that the microstructure of the Welding Nugget Zone (WNZ) is fine equiaxed grains. From the surface of the plate to the center of welding seam, the grain sizes are 16 μm, 13 μm, and 5 μm, respectively, and the proportions of high angle grain boundaries are 77.2%, 76.3%, and 72.5%, respectively. The strengthening phase of WNZ is mainly "GP zone" and β″. The grain of the Thermo-Mechanically Affected Zone (TMAZ) is elongated and there is a high density dislocation. The microhardness in the thickness direction indicates that the hardness curve of the center overlap area of the weld is "V" type, the lowest hardness value appears in the double-sided welding overlap area, while the hardness curve of the other area is "W" type,. The samples are all broken in the area where TMAZ and Heat Affected Zone (HAZ) meet. The tensile strengths from the surface to the center overlap in the thickness direction are 211 MPa, 201 MPa, and 180 MPa, which gradually decrease. The center overlap zone has the lowest tensile strength, but its elongation is the highest, which is about 69% of the base metal. The fracture surfaces were distributed with dimples of different sizes, and fractures in all tensile specimens were ductile fracture.

Key words: metallic materials, 6082 aluminum alloy, friction stir welding, ultra-thickness plate, microstructure, propertie

CLC Number: 

  • TG456.9

Fig.1

Distribution of microhardness experimental positions"

Fig.2

Macroscopic morphology of weld cross section"

Fig.3

Optical microscopic morphology of "S" line"

Fig.4

Optical microstructure of different regions of FSW joint"

Fig.5

EBSD maps of microstructure at various depths in WNZ"

Fig.6

Misorientation angle distribution at various depths in the WNZ"

Fig.7

TEM images of friction stir welded joint"

Fig.8

Microhardness profiles of welded joint along welding thickness direction"

Fig.9

Tensile test results of FSW joints"

Fig.10

SEM image of tensile fracture of welded joint"

Fig.11

Bending shape of FSW joint"

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