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金属学报  2017, Vol. 53 Issue (12): 1651-1658    DOI: 10.11900/0412.1961.2017.00025
  本期目录 | 过刊浏览 |
刘奋军1,2, 傅莉1,3,4(), 陈海燕1,3,4
1 西北工业大学材料学院 西安 710072
2 榆林学院能源工程学院 榆林 719000
3 西北工业大学凝固技术国家重点实验室 西安 710072
4 西北工业大学陕西省摩擦焊接工程技术重点实验室 西安 710072
Microstructures and Mechanical Properties of Thin Plate Aluminium Alloy Joint Prepared by High Rotational Speed Friction Stir Welding
Fenjun LIU1,2, Li FU1,3,4(), Haiyan CHEN1,3,4
1 School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an 710072, China
2 College of Energy Engineering, Yulin University, Yulin 719000, China
3 State Key Laboratory of Solidification, Northwestern Polytechnical University, Xi'an 710072, China
4 Shaanxi Key Laboratory of Friction Welding Technologies, Northwestern Polytechnical University, Xi'an 710072, China
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采用高转速微型搅拌摩擦焊接工艺实现了0.8 mm厚6061-T6铝合金薄板对接。利用OM、SEM、TEM及EBSD等测试技术探讨了高转速对接头微观组织及力学性能的影响规律。结果表明,高转速焊接6061-T6薄板时,焊缝表面成型良好,焊缝各区域组织呈连续均匀过渡。与常规搅拌摩擦焊相比,高转速工艺下,焊缝区β-Mg2Si、S相(Al2CuMg)和Al8Fe2Si析出相数量增多,特别是长条状β-Mg2Si数量增多,焊缝区显微硬度值明显提升;转速8000 r/min、焊速1500 mm/min条件下,接头最大抗拉强度高达301.8 MPa,是母材抗拉强度(351.7 MPa)的85.8%;转速对6061-T6铝合金超薄板高转速搅拌摩擦焊对接接头抗拉强度影响较小,接头断裂模式为脆性断裂为主的韧-脆混合断裂。

关键词 6061-T6铝合金薄板高转速FSW组织抗拉强度    

Aluminium alloys were widely applied in rail transit, ships and aerospace owing to their unique properties, such as low density, high strength and stiffness, outstanding corrosion resistance and low temperature performance. As a type of structure material, aluminium alloy joining was inevitable. However, these alloys were often considered very difficult to weld using traditional fusion welding technique since the welding seams were often accompanied with metallurgical defects, large deformation and stress. Friction stir welding (FSW), an innovative solid-state welding technology invented at the welding institute (TWI), was seen by designers as an effective joining methods in welding aluminium alloys due to low heat input, small stress-strain and environment friendly. In this work, 0.8 mm thick plate of 6061-T6 aluminium alloy was successfully welded by use of high rotational speed fiction stir welding technology. The microstructure and mechanical property of the butt joints prepared by high rotational speed friction stir welding were analysed in detail. The results show that the well surface topography and excellent bonding interface existed in the nugget zone (NZ) were observed. Both of the microhardness of the weld seam was lower than that of the substrate. The lowest microhardness of the butt joints located between the thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ). Compared with the conventional rotational speed, the number of β-Mg2Si, Al2CuMg and Al8Fe2Si precipitated phases existed in the NZ was more, which made the microhardness in the NZ improved significantly. The rod-shaped precipitates (Mg2Si) have the greatest influence on the microhardness. The excellent mechanical properties were obtained at the rotational speed of 8000 r/min and welding speed of 1500 mm/min. The maximum tensile strength was 301.8 MPa, which was 85.8% of the as-received 6061-T6 (351.7 MPa). And the toughness-brittleness fracture mode appeared.

Key wordsthin plate 6061-T6 aluminium alloy    high rotational speed    friction stir welding (FSW)    microstructure    tensile property
收稿日期: 2017-01-19      出版日期: 2017-06-05
ZTFLH:  TG146.2  

作者简介 刘奋军,男,1982年生,博士生


刘奋军, 傅莉, 陈海燕. 铝合金薄板高转速搅拌摩擦焊接头组织与力学性能[J]. 金属学报, 2017, 53(12): 1651-1658.
Fenjun LIU, Li FU, Haiyan CHEN. Microstructures and Mechanical Properties of Thin Plate Aluminium Alloy Joint Prepared by High Rotational Speed Friction Stir Welding. Acta Metall Sin, 2017, 53(12): 1651-1658.

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图1  6061-T6铝合金薄板搅拌摩擦焊(FSW)示意图及拉伸试样取样图
图2  不同转速下6061-T6铝合金薄板FSW焊缝表面成型宏观形貌
图3  不同转速下6061-T6铝合金薄板FSW接头宏观形貌
图4  不同转速下6061-T6铝合金FSW接头微观组织
图5  不同转速下6061-T6铝合金FSW接头析出相形貌及分布明场像
图6  转速8000 r/min下6061-T6铝合金FSW接头不同区域(图3b)晶粒分布特征
图7  图6中6061-T6铝合金FSW接头不同位置处晶粒分布
图8  不同转速下6061-T6铝合金FSW接头显微硬度分布
图9  转速8000 r/min下6061-T6铝合金薄板FSW接头焊核区晶界分布
ω / (rmin-1) v / (mmmin-1) σUTS / MPa σYS / MPa δ / %
0 0 351.7 296.8 21.50
2000 300 239.0 179.2 4.80
7000 1500 289.4 207.8 4.88
8000 1500 301.8 216.6 5.39
9000 1500 300.8 213.0 5.44
10000 1500 292.6 205.7 5.31
11000 1500 292.2 201.8 5.49
表1  6061-T6母材及不同转速下FSW对接接头拉伸性能
图10  转速8000 r/min下6061-T6铝合金FSW接头拉伸断口形貌
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