鋁合金薄板高轉(zhuǎn)速攪拌摩擦焊接頭組織與力學(xué)性能

鋁合金薄板高轉(zhuǎn)速攪拌摩擦焊接頭組織與力學(xué)性能Microstructure and mechanical property of thin plate aluminium alloy joint prepared by high rotation speed friction stir welding

采用高轉(zhuǎn)速微型攪拌摩擦焊接工藝實(shí)現(xiàn)了0.8 mm厚6061-T6鋁合金薄板對接。利用OM、SEM、TEM及EBSD等測試技術(shù)探討了高轉(zhuǎn)速對接頭微觀組織及力學(xué)性能的影響規(guī)律。結(jié)果表明，高轉(zhuǎn)速焊接6061-T6薄板時(shí)，焊縫表面成型良好，焊縫各區(qū)域組織呈連續(xù)均勻過渡。與常規(guī)攪拌摩擦焊相比，高轉(zhuǎn)速工藝下，焊縫區(qū)β-Mg2Si、S相(Al2CuMg)和Al8Fe2Si析出相數(shù)量增多，特別是長條狀β-Mg2Si數(shù)量增多，焊縫區(qū)顯微硬度值明顯提升；轉(zhuǎn)速8000 r/min，焊速1500 mm/min條件下，接頭最大抗拉強(qiáng)度高達(dá)301.8 MPa，是母材抗拉強(qiáng)度(351.7 MPa)的85.8%；轉(zhuǎn)速對6061-T6鋁合金超薄板高轉(zhuǎn)速攪拌摩擦焊對接接頭抗拉強(qiáng)度影響較小，接頭斷裂模式為脆性斷裂為主的韌-脆混合斷裂。

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 due to 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 the work, 0.8 mm thick plate of 6061-T6 aluminium alloy was successfully welded by use of high rotation speed fiction stir welding technology. The microstructure and mechanical property of the butt joints prepared by high rotation speed friction stir welding were analysed in detail. The results shown 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.

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