Microstructure and Mechanical Properties of 7A60-T6 Ultrahigh Strength Aluminium Alloy Friction Stir Welded Joints
摘 要
采用搅拌摩擦焊方法对6 mm厚7A60-T6超高强铝合金进行了焊接试验,分析讨论了接头的显微组织和力学性能。结果表明: 接头焊核区组织发生了动态再结晶,形成了细小的等轴再结晶晶粒,同时析出相大部分固溶入基体,热影响区晶粒粗化,在晶界处析出大量的析出相,前进侧热机影响区晶粒发生了较大程度的变形,后退侧晶粒变形程度较小; 在旋转速率为300 r·min-1、焊接速率为100 mm·min-1或旋转速率为600 r·min-1、焊接速率为300 mm·min-1时,接头的抗拉强度分别达到了465 MPa和464 MPa,可达母材抗拉强度的 70%; 接头微观断口中存在大量的小韧窝且韧窝较浅偏脆性,其断裂形式为韧性为主脆性为辅的混合型断裂; 接头上表面的显微硬度高于接头横截面的硬度,焊核区上部硬度高于下部硬度。
Abstract
Microstructures and mechanical properties of the whole specimen in 6 mm thickness TA60-T6 aluminium alloy plate joints obtained by friction stir welding (FSW) were studied. The results show that fine equiaxed and recrystallized grains could be observed in the weld nugget zone(WNZ), and the segregation phases mostly dissolved into the matrix. The microstructure of the heat affected zone(HAZ) consisted of coarse bar-shape recovery grain, and a large number of segregation phases appeared at the grain boundaries. Microstructure of the thermo-mechanically affected zone(TMAZ) on advancing side consisted of highly deformed grains, and small deformation on retreating side. When the rotating speed was 300 r·min-1 and the welding speed was 100 mm·min-1 or the rotating speed was 600 r·min-1 and the welding speed was 300 mm·min-1, the good weld was achieved, and the tensile strength of the joint reached 465 MPa and 464 MPa, about 70% of the ultimate strength of the base metal. The fracture analysis show that there were lots of low mesh dimples, the fracture mode of the joint was ductile/brittle mixed fracture. The micro-hardness of the top surface of the FSW joint was higher than that of the transversal section, and the micro-hardness of the weld nugget zone presented an ascending trend form bottom to top.
中图分类号 TG453
所属栏目 试验与研究
基金项目 国防基金资助项目(KZ101302117)
收稿日期 2012/10/29
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备注董继红(1982-),男,工程师,硕士。
引用该论文: DONG Ji-hong,DONG Chun-lin,LUAN Guo-hong. Microstructure and Mechanical Properties of 7A60-T6 Ultrahigh Strength Aluminium Alloy Friction Stir Welded Joints[J]. Physical Testing and Chemical Analysis part A:Physical Testing, 2013, 49(8): 516~521
董继红,董春林,栾国红. 7A60-T6超高强铝合金搅拌摩擦焊接头的组织及性能[J]. 理化检验-物理分册, 2013, 49(8): 516~521
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【3】DUMONT D,DESCHAMPS A,BRECHET Y. On the relationship between microstructure,strength and toughness in AA7050 aluminum alloy[J]. Materials Science and Engineering A,2003,356(1/2):326-336.
【4】WU Y L,FORES F H,ALVAREZ A,et al. Microstructure and properties of a new super high-strength Al-Zn-Mg-Cu alloy C912[J]. Materials and Design,1997,18(4/6):211-215.
【5】SHA G,ALFRED G. Early-stage precipitation in Al-Zn-Mg-Cu alloy(7050)[J]. Acta Materialia,2004,52(15):4503-4516.
【6】THOMAS W M T,NICHOLAS E D,NICHOLAS J C,et al. Friction stir butt welding:UK,PCT/GB92/02203[P]. 1991-12-01.
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【8】SUTTON M A,REYNOLDS A P,HUBBARD C R,et al. A study of residual stresses and microstructure in 2024 aluminum friction stir butt welds[J]. Journal of Engineering Materials and Technology,2003,124:215-221.
【9】BUSSU G,IVRINGP E. The role of residual stress and heat affected zone properties on fatigue crack propagation in friction stir welded 2024-T351 aluminum joints[J]. International Journal of Fatigue,2003,25:77-78.
【10】董继红,佟健华,郭晓娟,等. 30 mm 7A05铝合金搅拌摩擦焊接头组织及力学性能[J]. 焊接学报,2012,33(4):65-68.
【11】栾国红,NORTH T H,郭德伦,等. 铝合金搅拌摩擦焊接头行为分析[J]. 焊接学报,2002,23(6): 62-66.
【12】LI A,BROWN M W,RODOPOULOS C A,et al. Characterization of 2024-T351 friction stir welding joints[J]. Journal of Failure Analysis and Prevention,2006,20(4):83-96.
【13】KANG S H,HAN H N,OH K H,et al. Investigation of material flow and texture evolution in friction-stir welded aluminum alloy[J]. Metals and Materials International,2009,15(6):1027-1031.
【14】周鹏展,钟掘,贺地球. 7A52铝合金厚板搅拌摩擦焊[J]. 中国有色金属学报,2006,16(6):964-968.
【15】JATA K V,SANKRAN K K,RUSCHAU J J. Friction stir welding effects on microstructure and fatigue of aluminum alloy 7050-T7451[J]. Metallurgical and Materials Transactions A,2000,31:2181-2192.
【16】SU J Q,NELSON T W,MISHRA R,et al. Microstructure investigation of friction stir welded 7050-T651 aluminum[J]. Acta Materialia,2003,51:713-729.
【17】何小青,熊柏青,孙泽明,等. 喷射成形7A60合金的微观组织与力学性能研究[J]. 中国有色金属学报,2007,31(2):137-141.
【18】徐伟峰,刘金合,栾国红,等. 厚板铝合金搅拌摩擦焊接头显微组织与力学性能响[J]. 金属学报,2008,44(11):1404-1408.
【19】SATO Y S,KOKAWA H,ENMOTO M. Microstructural evolution of 6063 aluminum during friction stir welding[J]. Metallurgical and Materials Tran-saction A,1999,30(9):2429-2437.
【20】杨洪涛,陆政,顾家琳. 7A60超高强铝合金流动应力的研究[J]. 航空材料学报,2005,25(2):12-15.
【21】秦占领,刑丽,柯黎明,等. 7A09铝合金厚板搅拌摩擦焊接头显微组织与性能研究[J]. 南昌航空大学学报,2007,21(2):15-20.
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