SiC_p/6092Al复合材料搅拌摩擦焊接头的疲劳行为研究
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摘要
为获得高质量、疲劳性能优异的SiCp/6092Al复合材料搅拌摩擦焊接头,对3 mm厚的T6态SiCp/6092Al复合材料轧制板材分别在50 mm/min的低焊速和800 mm/min的高焊速下进行搅拌摩擦焊接,转速恒为1000 r/min,研究焊速对接头的组织演变及拉伸性能、高周疲劳性能的影响。结果表明,高焊速接头表面"鱼鳞纹"较明显,且横截面方向的焊核区形貌与低焊速接头具有一定差异。焊速增加显著提高了FSW接头的硬度和拉伸强度,而对于未打磨表面的接头却未能提高接头的疲劳极限,低焊速下接头的高周疲劳极限为150 MPa,高焊速下接头的高周疲劳极限降为140 MPa。不同循环应力加载下,试样表现出不同的断裂方式。高应力下,低焊速接头由表面"鱼鳞纹"凹痕引起疲劳断裂,而高焊速接头是由焊核区底部的涡旋区流动不充分引起断裂。在低应力下,未打磨试样均由接头表面"鱼鳞纹"凹痕引起疲劳断裂,三维表面形貌显示高焊速接头表面粗糙度较大是造成疲劳极限较低的原因。与未打磨试样相比,经过打磨抛光后的接头光滑表面试样的疲劳极限提高了40～65 MPa,且高焊速下的光滑试样表现出更高的疲劳极限(205 MPa),光滑表面接头在疲劳测试时均在最低硬度区及其附近区域发生断裂。
Al matrix composites(AMCs) have been used in the aerospace and automotive industries due to the desirable properties including high specific strength, superior wear resistance and low thermal expansion. However, the traditional fusion welding process of AMCs usually brings defects such as pores, particles segregation and detrimental phases, which limits the application of AMCs. So more and more attentions are paied on friction stir welding(FSW), a solid state welding method possessing great potential in the welding of AMCs. In this work, to acquire high quality and excellent fatigue property of friction stir welded SiCp/6092 Al composite joint, 3 mm-thick rolled SiCp/6092 Al composite plates with T6 state were conducted by FSW at a constant rotational rate of 1000 r/min, and at a low welding speed of50 mm/min and a high welding speed of 800 mm/min, respectively. Microstructure evolution, mechanical properties and high cycle fatigue behavior of the FSW joints were evaluated. The results showed that high welding speed resulted in a much rougher surface of scale-like ripple and the morphology of the nugget zone was different from that of the joint at low welding speed. Significant enhancement of the hardness and tensile strength were achieved in the joints at the high welding speed, but the fatigue properties were not improved for the joints with unpolished surfaces. The fatigue limit of the joint at low welding speed was 150 MPa, however the fatigue limit reduced to 140 MPa at the high welding speed. For the joints with polished surfaces, obviously enhanced fatigue limit was achieved at the high welding speed of800 mm/min compared to that of the joint at the low welding speed of 50 mm/min. Different fracture characteristics were observed in the specimens with unpolished surfaces at various cyclic stress loading. Under a low cyclic stress loading, crack initiated at the scale-like ripple on the surface of the specimen; under a high cyclic stress loading, crack also initiated at the scale-like ripple at the low welding speed, while the crack initiated at the swirl zone in the bottom of the nugget zone at the high welding speed. The results of three-dimension surface topography showed that a large surface roughness was achieved on the surface of the joint at the high welding speed, resulting in lower fatigue limit compared to that of the joint at the low welding speed. For the specimens with polished surfaces, the fatigue limit was improved by40～65 MPa compared to that of the specimens with unpolished surfaces. In this case, a high fatigue limit of 205 MPa was obtained in the joint at the high welding speed of 800 mm/min, and all the specimens failed at the lowest hardness zone and nearby.
Al matrix composites(AMCs) have been used in the aerospace and automotive industries due to the desirable properties including high specific strength, superior wear resistance and low thermal expansion. However, the traditional fusion welding process of AMCs usually brings defects such as pores, particles segregation and detrimental phases, which limits the application of AMCs. So more and more attentions are paied on friction stir welding(FSW), a solid state welding method possessing great potential in the welding of AMCs. In this work, to acquire high quality and excellent fatigue property of friction stir welded SiCp/6092 Al composite joint, 3 mm-thick rolled SiCp/6092 Al composite plates with T6 state were conducted by FSW at a constant rotational rate of 1000 r/min, and at a low welding speed of50 mm/min and a high welding speed of 800 mm/min, respectively. Microstructure evolution, mechanical properties and high cycle fatigue behavior of the FSW joints were evaluated. The results showed that high welding speed resulted in a much rougher surface of scale-like ripple and the morphology of the nugget zone was different from that of the joint at low welding speed. Significant enhancement of the hardness and tensile strength were achieved in the joints at the high welding speed, but the fatigue properties were not improved for the joints with unpolished surfaces. The fatigue limit of the joint at low welding speed was 150 MPa, however the fatigue limit reduced to 140 MPa at the high welding speed. For the joints with polished surfaces, obviously enhanced fatigue limit was achieved at the high welding speed of800 mm/min compared to that of the joint at the low welding speed of 50 mm/min. Different fracture characteristics were observed in the specimens with unpolished surfaces at various cyclic stress loading. Under a low cyclic stress loading, crack initiated at the scale-like ripple on the surface of the specimen; under a high cyclic stress loading, crack also initiated at the scale-like ripple at the low welding speed, while the crack initiated at the swirl zone in the bottom of the nugget zone at the high welding speed. The results of three-dimension surface topography showed that a large surface roughness was achieved on the surface of the joint at the high welding speed, resulting in lower fatigue limit compared to that of the joint at the low welding speed. For the specimens with polished surfaces, the fatigue limit was improved by40～65 MPa compared to that of the specimens with unpolished surfaces. In this case, a high fatigue limit of 205 MPa was obtained in the joint at the high welding speed of 800 mm/min, and all the specimens failed at the lowest hardness zone and nearby.
引文
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[7] Jiang X Q, Wynne B P, Martin J. Variant selection in stationary shoulder friction stir welded Ti-6Al-4V alloy[J]. J. Mater. Sci.Technol., 2018, 34:198
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[9] Wu L H, Nagatsuka K, Nakata K. Achieving superior mechanical properties in friction lap joints of copper to carbon-fiber-reinforced plastic by tool offsetting[J]. J. Mater. Sci. Technol., 2018, 34:1628
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[14] Dong P, Li H M, Sun D Q, et al. Effects of welding speed on the microstructure and hardness in friction stir welding joints of6005A-T6 aluminum alloy[J]. Mater. Des., 2013, 45:524
[15] Li Y Z, Wang Q Z, Xiao B L, et al. Effect of welding parameters and B4C contents on the microstructure and mechanical properties of friction stir welded B4C/6061Al joints[J]. J. Mater. Process.Technol., 2018, 251:305
[16] Ceschini L, Boromei I, Minak G, et al. Effect of friction stir welding on microstructure, tensile and fatigue properties of the AA7005/10 vol.%Al2O3pcomposite[J]. Compos. Sci. Technol.,2007, 67:605
[17] Wang D, Wang Q Z, Xiao B L, et al. Achieving friction stir welded SiCp/Al-Cu-Mg composite joint of nearly equal strength to base material at high welding speed[J]. Mater. Sci. Eng., 2014, A589:271
[18] Pirondi A, Collini L. Analysis of crack propagation resistance of Al-Al2O3particulate-reinforced composite friction stir welded butt joints[J]. Int. J. Fatigue, 2009, 31:111
[19] Ni D R, Chen D L, Xiao B L, et al. Residual stresses and high cycle fatigue properties of friction stir welded SiCp/AA2009 composites[J]. Int. J. Fatigue, 2013, 55:64
[20] Minak G, Ceschini L, Boromei I, et al. Fatigue properties of friction stir welded particulate reinforced aluminium matrix composites[J]. Int. J. Fatigue, 2010, 32:218
[21] James M N, Bradley G R, Lombard H, et al. The relationship between process mechanisms and crack paths in friction stir welded5083-H321 and 5383-H321 aluminium alloys[J]. Fatigue Fract.Eng. Mater. Struct., 2005, 28:245
[22] Chen X G, da Silva M, Gougeon P, et al. Microstructure and mechanical properties of friction stir welded AA6063-B4C metal matrix composites[J]. Mater. Sci. Eng., 2009, A518:174
[23] Liu F J, Fu L, Chen H Y. Microstructures and mechanical properties of thin plate aluminium alloy joint prepared by high rotational speed friction stir welding[J]. Acta Metall. Sin., 2017, 53:1651(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, 53:1651)
[24] Liu F C, Ma Z Y. Influence of tool dimension and welding parameters on microstructure and mechanical properties of friction-stirwelded 6061-T651 aluminum alloy[J]. Metall. Mater. Trans.,2008, 39A:2378
[25] Frigaard?, Grong?, Midling O T. A process model for friction stir welding of age hardening aluminum alloys[J]. Metall. Mater.Trans., 2001, 32A:1189
[26] Schmidt H, Hattel J. A local model for the thermomechanical conditions in friction stir welding[J]. Model. Simul. Mater. Sci. Eng.,2005, 13:77
[27] Kim J H, Barlat F, Kim C, et al. Themo-mechanical and microstructural modeling of friction stir welding of 6111-T4 aluminum alloys[J]. Metall. Mater. Int., 2009, 15:125
[28] Zeng X H, Xue P, Wang D, et al. Realising equal strength welding to parent metal in precipitation-hardened Al-Mg-Si alloy via low heat input friction stir welding[J]. Sci. Technol. Weld. Joining,2018, 23:478
[29] Suresh S. Fatigue of Materials[M]. 2nd Ed., Cambridge:Cambridge University Press, 1998:259
[30] Zhang Z, Xiao B L, Wang D, et al. Effect of alclad layer on material flow and defect formation in friction-stir-welded 2024 aluminum alloy[J]. Metall. Mater. Trans., 2011, 42A:1717
[31] Proudhon H, Fouvry S, Buffiere J Y. A fretting crack initiation prediction taking into account the surface roughness and the crack nucleation process volume[J]. Int. J. Fatigue, 2005, 27:569
[32] Murakami Y, Endo M. Effects of defects, inclusions and inhomogeneities on fatigue strength[J]. Int. J. Fatigue, 1994, 16:163
[33] Itoga H, Tokaji K, Nakajima M, et al. Effect of surface roughness on step-wise S-N characteristics in high strength steel[J]. Int. J.Fatigue, 2003, 25:379
[34] Arbegast W J. A flow-partitioned deformation zone model for defect formation during friction stir welding[J]. Scr. Mater., 2008,58:372
[35] Arbegast W J. Modeling friction stir joining as a metalworking process[A]. Hot Deformation of Aluminum Alloys III[C]. San Diego:Wiey-TMS, 2003:313
[36] Dickerson T L, Przydatek J. Fatigue of friction stir welds in aluminium alloys that contain root flaws[J]. Int. J. Fatigue, 2003, 25:1399
[37] Zhou L, Wang T, Zhou W L, et al. Microstructural characteristics and mechanical properties of 7050-T7451 aluminum alloy friction stir-welded joints[J]. J. Mater. Eng. Perform., 2016, 25:2542
[2] Dai J, Liu Z, Yang L, et al. Research on pulsed laser welding of TiB2-enhanced aluminum matrix composites[J]. Int. J. Adv. Manuf.Tech., 2016, 85:157
[3] Xue P, Ni D R, Wang D, et al. Effect of friction stir welding parameters on the microstructure and mechanical properties of the dissimilar Al-Cu joints[J]. Mater. Sci. Eng., 2011, A528:4683
[4] Wang G Q, Zhao Y H, Hao Y F. Friction stir welding of highstrength aerospace aluminum alloy and application in rocket tank manufacturing[J]. J. Mater. Sci. Technol., 2018, 34:73
[5] Shang Q, Ni D R, Xue P, et al. Improving joint performance of friction stir welded wrought Mg alloy by controlling non-uniform deformation behavior[J]. Mater. Sci. Eng., 2017, A707:426
[6] Xue P, Xiao B L, Zhang Q, et al. Achieving friction stir welded pure copper joints with nearly equal strength to the parent metal via additional rapid cooling[J]. Scr. Mater., 2011, 64:1051
[7] Jiang X Q, Wynne B P, Martin J. Variant selection in stationary shoulder friction stir welded Ti-6Al-4V alloy[J]. J. Mater. Sci.Technol., 2018, 34:198
[8] Reynolds A P, Tang W, Gnaupel-Herold T, et al. Structure, properties, and residual stress of 304L stainless steel friction stir welds[J].Scr. Mater., 2003, 48:1289
[9] Wu L H, Nagatsuka K, Nakata K. Achieving superior mechanical properties in friction lap joints of copper to carbon-fiber-reinforced plastic by tool offsetting[J]. J. Mater. Sci. Technol., 2018, 34:1628
[10] Feng A H, Xiao B L, Ma Z Y. Effect of microstructural evolution on mechanical properties of friction stir welded AA2009/SiCpcomposite[J]. Compos. Sci. Technol., 2008, 68:2141
[11] Wang D, Wang Q Z, Xiao B L, et al. Effect of heat treatment before welding on microstructure and mechanical properties of friction stir welded SiCp/Al-Cu-Mg composite joints[J]. Acta Metall.Sin., 2014, 50:489(王东,王全兆,肖伯律等.焊前热处理状态对SiCp/Al-Cu-Mg复合材料搅拌摩擦焊接头微观组织和力学性能的影响[J].金属学报, 2014, 50:489)
[12] Sato Y S, Kokawa H, Enomoto M, et al. Microstructural evolution of 6063 aluminum during friction-stir welding[J]. Metall. Mater.Trans., 1999, 30A:2429
[13] Wang B B, Chen F F, Liu F, et al. Enhanced Mechanical properties of friction stir welded 5083Al-H19 joints with additional water cooling[J]. J. Mater. Sci. Technol., 2017, 33:1009
[14] Dong P, Li H M, Sun D Q, et al. Effects of welding speed on the microstructure and hardness in friction stir welding joints of6005A-T6 aluminum alloy[J]. Mater. Des., 2013, 45:524
[15] Li Y Z, Wang Q Z, Xiao B L, et al. Effect of welding parameters and B4C contents on the microstructure and mechanical properties of friction stir welded B4C/6061Al joints[J]. J. Mater. Process.Technol., 2018, 251:305
[16] Ceschini L, Boromei I, Minak G, et al. Effect of friction stir welding on microstructure, tensile and fatigue properties of the AA7005/10 vol.%Al2O3pcomposite[J]. Compos. Sci. Technol.,2007, 67:605
[17] Wang D, Wang Q Z, Xiao B L, et al. Achieving friction stir welded SiCp/Al-Cu-Mg composite joint of nearly equal strength to base material at high welding speed[J]. Mater. Sci. Eng., 2014, A589:271
[18] Pirondi A, Collini L. Analysis of crack propagation resistance of Al-Al2O3particulate-reinforced composite friction stir welded butt joints[J]. Int. J. Fatigue, 2009, 31:111
[19] Ni D R, Chen D L, Xiao B L, et al. Residual stresses and high cycle fatigue properties of friction stir welded SiCp/AA2009 composites[J]. Int. J. Fatigue, 2013, 55:64
[20] Minak G, Ceschini L, Boromei I, et al. Fatigue properties of friction stir welded particulate reinforced aluminium matrix composites[J]. Int. J. Fatigue, 2010, 32:218
[21] James M N, Bradley G R, Lombard H, et al. The relationship between process mechanisms and crack paths in friction stir welded5083-H321 and 5383-H321 aluminium alloys[J]. Fatigue Fract.Eng. Mater. Struct., 2005, 28:245
[22] Chen X G, da Silva M, Gougeon P, et al. Microstructure and mechanical properties of friction stir welded AA6063-B4C metal matrix composites[J]. Mater. Sci. Eng., 2009, A518:174
[23] Liu F J, Fu L, Chen H Y. Microstructures and mechanical properties of thin plate aluminium alloy joint prepared by high rotational speed friction stir welding[J]. Acta Metall. Sin., 2017, 53:1651(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, 53:1651)
[24] Liu F C, Ma Z Y. Influence of tool dimension and welding parameters on microstructure and mechanical properties of friction-stirwelded 6061-T651 aluminum alloy[J]. Metall. Mater. Trans.,2008, 39A:2378
[25] Frigaard?, Grong?, Midling O T. A process model for friction stir welding of age hardening aluminum alloys[J]. Metall. Mater.Trans., 2001, 32A:1189
[26] Schmidt H, Hattel J. A local model for the thermomechanical conditions in friction stir welding[J]. Model. Simul. Mater. Sci. Eng.,2005, 13:77
[27] Kim J H, Barlat F, Kim C, et al. Themo-mechanical and microstructural modeling of friction stir welding of 6111-T4 aluminum alloys[J]. Metall. Mater. Int., 2009, 15:125
[28] Zeng X H, Xue P, Wang D, et al. Realising equal strength welding to parent metal in precipitation-hardened Al-Mg-Si alloy via low heat input friction stir welding[J]. Sci. Technol. Weld. Joining,2018, 23:478
[29] Suresh S. Fatigue of Materials[M]. 2nd Ed., Cambridge:Cambridge University Press, 1998:259
[30] Zhang Z, Xiao B L, Wang D, et al. Effect of alclad layer on material flow and defect formation in friction-stir-welded 2024 aluminum alloy[J]. Metall. Mater. Trans., 2011, 42A:1717
[31] Proudhon H, Fouvry S, Buffiere J Y. A fretting crack initiation prediction taking into account the surface roughness and the crack nucleation process volume[J]. Int. J. Fatigue, 2005, 27:569
[32] Murakami Y, Endo M. Effects of defects, inclusions and inhomogeneities on fatigue strength[J]. Int. J. Fatigue, 1994, 16:163
[33] Itoga H, Tokaji K, Nakajima M, et al. Effect of surface roughness on step-wise S-N characteristics in high strength steel[J]. Int. J.Fatigue, 2003, 25:379
[34] Arbegast W J. A flow-partitioned deformation zone model for defect formation during friction stir welding[J]. Scr. Mater., 2008,58:372
[35] Arbegast W J. Modeling friction stir joining as a metalworking process[A]. Hot Deformation of Aluminum Alloys III[C]. San Diego:Wiey-TMS, 2003:313
[36] Dickerson T L, Przydatek J. Fatigue of friction stir welds in aluminium alloys that contain root flaws[J]. Int. J. Fatigue, 2003, 25:1399
[37] Zhou L, Wang T, Zhou W L, et al. Microstructural characteristics and mechanical properties of 7050-T7451 aluminum alloy friction stir-welded joints[J]. J. Mater. Eng. Perform., 2016, 25:2542
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