Influence of welding defects on fatigue behavior of dissimilar aluminum alloy TIG butt joint
-
摘要:
以5A06-O/7A05-T6异种铝合金钨极氩弧焊(TIG)对接接头为对象,通过疲劳试验数据和断口形貌分析,研究了气孔缺陷和未熔合缺陷对焊接接头疲劳性能的影响规律及机理。结果表明:气孔缺陷和未熔合缺陷对5A06-O/7A05-T6对接接头的疲劳性能均产生不利影响,且缺陷的大小、位置与载荷的交互作用是影响疲劳裂纹提前萌生的主要因素,同一应力水平下,疲劳裂纹更易萌生于尺寸较大且位置更接近于材料表面的焊接缺陷处,而随着应力水平的降低,焊接缺陷对焊接接头疲劳性能的不利影响更为显著;与气孔缺陷相比,未熔合缺陷边缘的应力集中效应更明显,更易导致疲劳裂纹萌生,且焊接接头组织相较于焊接母材组织更脆,疲劳裂纹以穿晶和沿晶形式交替扩展,使疲劳寿命进一步缩短。
-
关键词:
- 铝合金 /
- 钨极氩弧焊(TIG) /
- 焊接缺陷 /
- 疲劳 /
- SEM
Abstract:Fatigue tests and fracture morphology analyses were performed to determine the influence law and mechanism of pore defect and incomplete fusion defect on the fatigue performance of 5A06-O/7A05-T6 dissimilar aluminum alloy TIG butt joint. The results show that both pore defect and incomplete fusion defect have adverse effects on the fatigue properties of 5A06-O/7A05-T6 butt joint, and the interaction between the size and location of defects and the load is the main factor affecting the early initiation of fatigue cracks. Fatigue cracks are more likely to initiate at the welding defects with larger size and closer to the material surface under the same stress level, and the interaction between welding defects and fatigue loading increases with the decrease of stress level, and ultimately decreases the fatigue strength. Compared with pore defect, the effect of stress concentration at the edge of incomplete fusion defect is more significant, which is more likely to cause fatigue crack initiation, the microstructure of welded joint is more brittle than that of welding base metal, and the fatigue crack propagates alternately in the transgranular and intergranular form, which further shortens the fatigue life.
-
Key words:
- aluminum alloy /
- TIG /
- welding defects /
- fatigue /
- SEM
-
表 1 5A06-O/7A05-T6焊接母材及焊丝的力学性能
Table 1. Mechanical properties of 5A06-O/7A05-T6 welding base metal and welding wire
材料 σb/MPa σs/MPa δ/% 5A06-O 356.4 161.8 21.14 7A05-T6 414.4 311.6 13.56 5A06-O/7A05-T6 281.08 157.33 11.43 注: σb为强度极限,σs为屈服极限,δ为延伸率。 表 2 5A06-O/7A05-T6焊接母材及焊丝的化学成分
Table 2. Chemical composition of 5A06-O/7A05-T6 welding base metal and welding wire
材料 元素含量 5A06-O Mg Mn Zn Fe Si Cu Ti Al 6.2 0.62 0.23 0.13 0.12 0.11 0.03 Bal. 7A05-T6 Zn Mg Mn Cu Fe Si Ti Al 4.58 1.37 0.22 0.16 0.15 0.08 0.04 Bal. ER5356 Mg Fe Mn Ti Si Zn Cu Al 4.59 0.13 0.12 0.1 0.04 0.01 0.001 Bal. 注: Bal.表示Al元素的含量为除了表中已经列出的元素含量外剩下的化学元素含量。 表 3 试验环境
Table 3. Test environments
环境 温度/℃ 试样 加载方式 干燥大气 25±3 5A06-O/7A05-T6
对接接头(气孔缺陷)T-T恒幅加载 干燥大气 25±3 5A06-O/7A05-T6
对接接头(未熔合缺陷)T-T恒幅加载 表 4 疲劳S-N曲线
Table 4. Fatigue S-N curves
试样 试验环境 S-N曲线 5A06-O 干燥大气 Smax6.02N=1.86×1019 7A05-T6 干燥大气 (Smax-240.3)1.56N=7.8×107 5A06-O/7A05-T6
焊接接头(气孔缺陷)干燥大气 Smax3.50N=1.08×1013 表 5 未熔合缺陷影响系数拟合曲线
Table 5. Fitting curves of influence coefficient of incomplete fusion defect
Smax/MPa 未熔合缺陷影响系数曲线 相关系数R2 120 y=0.047x+1.75 0.979 90 y=0.049x+1.84 0.997 60 y=0.056x+2.21 0.983 -
[1] 马青娜, 邵飞, 高磊. 铝合金焊接接头疲劳研究进展综述[J]. 建筑结构, 2018, 48(S2): 1037-1041. https://www.cnki.com.cn/Article/CJFDTOTAL-JCJG2018S2211.htmMA Q N, SHAO F, GAO L. Overview of research progress of fatigue of aluminum alloy butt joints[J]. Building Structure, 2018, 48(S2): 1037-1041(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JCJG2018S2211.htm [2] 李占明, 朱有利, 杜晓坤, 等. 铝合金手工GTAW焊接缺陷及其对疲劳性能的影响[J]. 热加工工艺, 2012, 41(15): 133-135. https://www.cnki.com.cn/Article/CJFDTOTAL-SJGY201215043.htmLI Z M, ZHU Y L, DU X K, et al. Effect of aluminum alloy welding defects in gas tungsten arc welding on fatigue properties[J]. Hot Working Technology, 2012, 41(15): 133-135(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-SJGY201215043.htm [3] 马思群, 谷理想, 袁永文, 等. 焊接缺陷对动车组铝合金车体疲劳寿命影响研究[J]. 铁道学报, 2014, 36(2): 42-48. doi: 10.3969/j.issn.1001-8360.2014.02.007MA S Q, GU L X, YUAN Y W, et al. Research on influence of welding defects on fatigue life of EMU aluminum-alloy car body[J]. Journal of the China Railway Society, 2014, 36(2): 42-48(in Chinese). doi: 10.3969/j.issn.1001-8360.2014.02.007 [4] ZHU C X, TANG X H, HE Y, et al. Effect of preheating on the defects and microstructure in NG-GMA welding of 5083 Al-alloy[J]. Journal of Materials Processing Technology, 2018, 251: 214-224. doi: 10.1016/j.jmatprotec.2017.08.037 [5] 邹东利, 陈向林, 肖大武, 等. 5A06铝合金激光焊接接头显微组织及缺陷分析[J]. 稀有金属材料与工程, 2019, 48(9): 2951-2956. https://www.cnki.com.cn/Article/CJFDTOTAL-COSE201909034.htmZOU D L, CHEN X L, XIAO D W, et al. Microstructure and defects analysis of 5A06 aluminium alloy laser butt joint[J]. Rare Metal Materials and Engineering, 2019, 48(9): 2951-2956(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-COSE201909034.htm [6] 王池权, 熊峻江, 马少俊, 等. 航空铝合金材料腐蚀裂纹扩展性能试验[J]. 北京航空航天大学学报, 2017, 43(5): 935-941. doi: 10.13700/j.bh.1001-5965.2016.0360WANG C Q, XIONG J J, MA S J, et al. Tests for corrosion crack propagation behavior of aeronautical aluminum alloys[J]. Journal of Beijing University of Aeronautics and Astronautics, 2017, 43(5): 935-941(in Chinese). doi: 10.13700/j.bh.1001-5965.2016.0360 [7] ZHANG B, CHEN W, POIRIER D R. Effect of solidification cooling rate on the fatigue life of A356.2-T6 cast aluminum alloy[J]. Fatigue and Fracture of Engineering Materials and Structures, 2000, 23(5): 417-423. doi: 10.1046/j.1460-2695.2000.00299.x [8] 王晨, 王贝贝, 薛鹏, 等. SiCp/6092Al复合材料搅拌摩擦焊接头的疲劳行为研究[J]. 金属学报, 2019, 55(1): 149-159. https://www.cnki.com.cn/Article/CJFDTOTAL-JSXB201901014.htmWANG C, WANG B B, XUE P, et al. Fatigue behavior of friction stir welded SiCp/6092Al composite[J]. Acta Metallurgica Sinica, 2019, 55(1): 149-159(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JSXB201901014.htm [9] 张红霞, 吴广贺, 闫志峰, 等. 5A06铝合金及其焊接接头的疲劳断裂行为[J]. 中国有色金属学报, 2013(2): 327-335. https://www.cnki.com.cn/Article/CJFDTOTAL-ZYXZ201302006.htmZHANG H X, WU G H, YAN Z F, et al. Fatigue fracture behavior of 5A06 aluminum alloy and its butt joint[J]. The Chinese Journal of Nonferrous Metals, 2013(2): 327-335(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-ZYXZ201302006.htm [10] 何超, 崔仕明, 刘永杰, 等. 气孔对铝合金焊接接头超长疲劳寿命的影响[J]. 焊接学报, 2014(11): 18-22. https://www.cnki.com.cn/Article/CJFDTOTAL-HJXB201411005.htmHE C, CUI S M, LIU Y J, et al. Arc behavior of A-MIG welding and microstructure of aluminum alloy butt joint[J]. Transactions of the China Welding Institution, 2014(11): 18-22(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-HJXB201411005.htm [11] 赵旭, 陈辉. 7N01铝合金平滑焊接接头疲劳性能研究[J]. 热加工工艺, 2016, 45(21): 183-186. https://www.cnki.com.cn/Article/CJFDTOTAL-SJGY201621051.htmZHAO X, CHEN H. Research on fatigue property of smooth weld joints in 7N01 aluminum alloy[J]. Hot Working Technology, 2016, 45(21): 183-186(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-SJGY201621051.htm [12] 宋哲, 吴圣川, 胡雅楠, 等. 冶金型气孔对熔化焊接7020铝合金疲劳行为的影响[J]. 金属学报, 2018, 54(8): 1131-1140. https://www.cnki.com.cn/Article/CJFDTOTAL-JSXB201808006.htmSONG Z, WU S C, HU Y N, et al. The influence of metallurgical pores on fatigue behaviors of fusion welded AA7020 joints[J]. Acta Metallurgica Sinica, 2018, 54(8): 1131-1140(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JSXB201808006.htm [13] 胡志力, 李锦, 万心勇, 等. 铝合金搅拌摩擦焊接头服役孔洞裂纹扩展规律[J]. 稀有金属材料与工程, 2019, 48(3): 892-897. https://www.cnki.com.cn/Article/CJFDTOTAL-COSE201903030.htmHU Z L, LI J, WAN X Y, et al. Crack propagation law of holes in aluminum alloy friction stir welding joint[J]. Rare Metal Materials and Engineering, 2019, 48(3): 892-897(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-COSE201903030.htm [14] 邓彩艳, 高仁, 龚宝明, 等. 7050铝合金搅拌摩擦焊接头超高周疲劳性能[J]. 焊接学报, 2018, 39(11): 114-118. doi: 10.12073/j.hjxb.2018390284DENG C Y, GAO R, GONG B M, et al. Research on ultra-high-cycle fatigue properties of 7050 aluminum alloy FSW butt joints[J]. Transactions of the China Welding Institution, 2018, 39(11): 114-118(in Chinese). doi: 10.12073/j.hjxb.2018390284 [15] 吴圣川, 谢成, 胡雅楠, 等. 中高强度铝合金熔化焊接接头的缺陷容限评价方法[J]. 机械工程学报, 2020, 56(8): 46-59. https://www.cnki.com.cn/Article/CJFDTOTAL-JXXB202008006.htmWU S C, XIE C, HU Y N, et al. Defect tolerance assessment method of fusion welded medium and high strength Al alloy joints[J]. Journal of Mechanical Engineering, 2020, 56(8): 46-59(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-JXXB202008006.htm [16] 孔令明, 杜双明, 韩赟, 等. 镁合金/不锈钢钨极氩弧焊熔钎焊接头结合界面微观组织分析[J]. 矿冶工程, 2017, 37(5): 118-121. doi: 10.3969/j.issn.0253-6099.2017.05.028KONG L M, DU S M, HAN Y, et al. Analysis of interface microstructure of TIG brazing joint of magnesium alloy and stainless steel[J]. Mining and Metallurgical Engineering, 2017, 37(5): 118-121(in Chinese). doi: 10.3969/j.issn.0253-6099.2017.05.028 [17] LIU F, LIU Y, WU Y. Effect of lattice matching degree and intermetallic compound on the properties of Mg/Al dissimilar material butt joints[J]. Science and Technology of Welding and Joining, 2017, 22(8): 719-725. doi: 10.1080/13621718.2017.1313584 [18] DU H G, LI Y J, XU X Y, et al. Analysis of microstructure and properties of Mg/Al dissimilar joints by GTAW with Al-Si filler wire[J]. Kovove Mater, 2015, 53: 113-118. http://smartsearch.nstl.gov.cn/paper_detail.html?id=f98823e4278982aa48ca90d5e65fcf77 [19] 饶文姬, 魏守征, 李志勇, 等. AZ31B/5A06脉冲熔化极氩弧焊焊缝组织特性[J]. 热加工工艺, 2019, 48(21): 26-30. https://www.cnki.com.cn/Article/CJFDTOTAL-SJGY201921008.htmRAO W J, WEI S Z, LI Z Y, et al. Microstructures of weld seam during pulsed metal inert-gas welding of AZ31B and 5A06 dissimilar alloys[J]. Hot Working Technology, 2019, 48(21): 26-30(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-SJGY201921008.htm [20] 杜红燕, 李亚江. AZ31/7005异种材料填丝GTAW焊接接头的组织与性能[J]. 材料工程, 2014(9): 14-19. https://www.cnki.com.cn/Article/CJFDTOTAL-CLGC201409004.htmDU H Y, LI Y J. Microstructures and properties of AZ31/7005 dissimilar joints by GTAW with filler wire[J]. Journal of Materials Engineering, 2014(9): 14-19(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-CLGC201409004.htm [21] 廖传清, 宿国友, 高艳芳, 等. 7075/5A06异种铝合金TIG焊接头的显微组织和力学性能[J]. 中国有色金属学报, 2015(1): 43-48. https://www.cnki.com.cn/Article/CJFDTOTAL-ZYXZ201501007.htmLIAO C Q, SU G Y, GAO Y F, et al. Microstructure and mechanical properties of 7075/5A06 dissimilar aluminum alloy joints made by TIG welding[J]. The Chinese Journal of Nonferrous Metals, 2015(1): 43-48(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-ZYXZ201501007.htm [22] 吕堂祺, 丁凯, 施睿贇, 等. 20钢-铝青铜焊接接头的组织和高周次疲劳性能研究[J]. 上海金属, 2020, 42(1): 13-16. https://www.cnki.com.cn/Article/CJFDTOTAL-SHJI202001003.htmLV T Q, DING K, SHI R Y, et al. Investigation on microstructure and high-cycle fatigue behavior of butt joint of 20 steel and albronze[J]. Shanghai Metals, 2020, 42(1): 13-16(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-SHJI202001003.htm [23] Standard Practice or conducting force controlled constant amplitude axial fatigue tests of materials: ASTM E466-2015[S]. America Society for Testing and Materials International, 2015. [24] 高镇同, 蒋新桐, 熊峻江, 等. 疲劳性能试验设计和数据处理[M]. 北京: 北京航空航天大学出版社, 1999: 21-23.GAO Z T, JIANG X T, XIONG J J, et al. Fatigue experiment design and data processing[M]. Beijing: Beihang University Press, 1999: 21-23(in Chinese). [25] 李宏伟, 姚为, 王志敏, 等. 激光焊接ZL114A/5A06异种铝合金接头组织及性能[J]. 宇航材料工艺, 2010, 40(6): 70-73. doi: 10.3969/j.issn.1007-2330.2010.06.017LI H W, YAO W, WANG Z M, et al. Microstructure and properties of dissimilar aluminum alloys ZL114A/5A06 joints by laser welding[J]. Aerospace Materials & Technology, 2010, 40(6): 70-73(in Chinese). doi: 10.3969/j.issn.1007-2330.2010.06.017 [26] 佟建华, 张坤, 林松, 等. 搅拌摩擦焊和熔化极气体保护焊6082铝合金疲劳性能分析[J]. 焊接学报, 2015, 36(7): 105-108. https://www.cnki.com.cn/Article/CJFDTOTAL-HJXB201507025.htmTONG J H, ZHANG K, LIN S, et al. Comparison of fatigue property of 6082 aluminum alloy joint by friction stir welding and metal inert-gas welding[J]. Transactions of the China Welding Institution, 2015, 36(7): 105-108(in Chinese). https://www.cnki.com.cn/Article/CJFDTOTAL-HJXB201507025.htm [27] WANG W K, CAO Z Q, SHI L, et al. Fatigue behavior investigation on dissimilar aluminum alloy ring butt joints in a new type sandwich high-pressure shell[J]. Materials Research Express, 2019, 6(6): 066534. doi: 10.1088/2053-1591/ab0b1a