试验选用ZK61, AZ31, AZ61和AZ91镁合金进行焊接凝固裂纹敏感性的分析. 首先进行了双速模式下的横向移动裂纹敏感性试验，获得了4种镁合金的临界横向移动速度，并对凝固裂纹敏感性进行了评估和排序：ZK61 > AZ31 > AZ61 > AZ91，与单速模式试验结果以及基于│dT/d(fS)1/2│max作为裂纹敏感指数得到的计算预测结果一致，验证了双速模式的横向移动裂纹敏感性试验用于评估镁合金凝固裂纹敏感性的有效性.凝固裂纹尖端及周边存在液相回填特征，ZK61镁合金的晶间回填液相呈非连续状且回填通道较窄，难以起到愈合裂纹效果，增大了凝固裂纹敏感性；AZ91镁合金液相回填通道宽度最大，有利于晶间液相回填，降低了凝固裂纹敏感性.
In present work, the widely used Mg alloys ZK61, AZ31, AZ61 and AZ91 were selected for investigating the solidification cracking susceptibility during welding. Transverse motion weldability (TMW) test in two-speed mode was used to evaluate the susceptibility of Mg alloys to solidification cracking during welding. The critical transverse moving speed was obtained and considered as an index to estimate the solidification cracking susceptibility of Mg alloys as ranking: ZK61 > AZ31 > AZ61 > AZ91. The ranking is consistent with the results of one-speed test and predicted results based on │dT/d(fS)1/2│max. It was shown that two-speed test of TMW is effective to evaluate the susceptibility of Mg alloys to solidification cracking. According to the backfilled liquid at the tip of or near the solidification cracking, the intergranular backfilled liquid of ZK61 is discontinuous and the channel is narrow, which is difficult to heal the crack and increases the solidification cracking susceptibility. The liquid backfilling channel of AZ91 is the widest, which is conducive to intergranular liquid backfilling and reduces the solidification crack susceptibility.
[1] Song J F, Pan F S, Jiang B, et al. A review on hot tearing of magnesium alloys[J]. Journal of Magnesium and Alloys, 2016, 4(3): 151-172.
[2] 闫志峰, 王卓然, 王树邦, 等. AZ31镁合金双面对称搅拌摩擦焊接头疲劳性能[J]. 焊接学报, 2022, 43(6): 61-68
Yan Zhifeng, Wang Zhuoran, Wang Shubang, et al. Fatigue properties of AZ31 magnesium alloy welded joint by double-sided friction stir welding[J]. Transactions of the China Welding Institution, 2022, 43(6): 61-68
[3] 陈怡, 郭龙涛, 祁同福, 等. 镁合金铸件氦-氩保护TIG焊修复工艺[J]. 焊接学报, 2021, 42(9): 35-41
Chen Yi, Guo Longtao, Qi Tongfu, et al. Repair process of magnesium alloy casting by He-Ar mixed gas TIG welding[J]. Transactions of the China Welding Institution, 2021, 42(9): 35-41
[4] Liu L M, Welding and joining of magnesium alloys[M]. Cambridge: Woodhead Publishing, 2010.
[5] Liu K, Kou S. Susceptibility of magnesium alloys to solidification cracking[J]. Science and Technology of Welding and Joining, 2020, 25(3): 251-257.
[6] Kou S. Welding metallurgy[M]. 3 rd edition. Hoboken N J: John Wiley and Sons, 2020.
[7] Kou S. A criterion for cracking during solidification[J]. Acta Materialia, 2015, 88: 366-374.
[8] Clyne T W, Davies G J. The influence of composition on solidification cracking susceptibility in binary alloy systems[J]. 1981, Br Foundryman, 74: 65 − 73
[9] Kou S. A simple index for predicting the susceptibility to solidification cracking[J]. Welding Journal, 2015, 94: 374s-388s.
[10] Liu J W, Kou S. Effect of diffusion on susceptibility to cracking during solidification[J]. Acta Materialia, 2015, 100: 359-368.
[11] Liu J W, Kou S. Susceptibility of ternary aluminum alloys to cracking during solidification[J]. Acta Materialia, 2017, 125: 513-523.
[12] Soysal T, Kou S. Predicting effect of filler metals on solidification cracking susceptibility of 2024 Al and 6061 Al[J]. Science and Technology of Welding and Joining, 2019, 24(6): 559-565.
[13] Soysal T, Kou S. Effect of filler metals on solidification cracking susceptibility of Al alloys 2024 and 6061[J]. Journal of Materials Processing Technology, 2019, 266: 421-428.
[14] Soysal T, Kou S. A simple test for solidification cracking susceptibility and filler metal effect[J]. Welding Journal, 2017, 96(10): 389s-401s.
[15] Soysal T, Kou S. A simple test for assessing solidification cracking susceptibility and checking validity of susceptibility prediction[J]. Acta Materialia, 2018, 143: 181-197.
[16] Savage W F, Lundin C D. The Varestraint test[J]. Welding Journal, 1965, 44(10): 433s-442s.
[17] Liu K, Yu P, Kou S. Solidification cracking susceptibility of stainless steels: new test and explanation[J]. Welding Journal, 2020, 99(10): 255s-270s.
[18] Adamiec J. Evaluation of susceptibility of the ZRE1 alloy to hot cracking in conditions of forced strain[J]. Archives of Foundry Engineering, 2010, 10(1): 345-350.
[19] Huang C J, Cheng C M, Chou C P, et al. Hot cracking in AZ31 and AZ61 magnesium alloy[J]. Journal of Materials Science & Technology, 2011, 27(7): 633-640.
[20] Kierzek A, Adamiec J. Evaluation of susceptibility to hot cracking of magnesium alloy joints in variable stiffness condition[J]. Archives of Metallurgy and Materials, 2011, 56(3): 759-767.
[21] Liu L M, Dong C. Gas tungsten-arc filler welding of AZ31 magnesium alloy[J]. Materials letters, 2006, 60(17-18): 2194-2197.
[22] Cao G P, Haygood I, Kou S. Onset of hot tearing in ternary Mg-Al-Sr alloy castings[J]. Metallurgical and Materials Transactions A, 2010, 41(8): 2139-2150.
[23] Cao G P, Kou S. Hot tearing of ternary Mg-Al-Ca alloy castings[J]. Metallurgical and Materials Transactions A, 2006, 37(12): 3647-3663.
[24] Cao G P, Kou S. Real-time monitoring of hot tearing in AZ91E magnesium casting[J]. Transactions of the American Foundry Society, 2007, 115: 7-34.
[25] Sun D X, Cui D L, Shi J T. Hot cracking and microstructure of welding joint of magnesium alloy AZ91D[J]. Advanced Materials Research, 2013, 753-755: 435-438.
[26] Zhou W, Long T Z, Mark C K. Hot cracking in tungsten inert gas welding of magnesium alloy AZ91D[J]. Materials Science and Technology, 2007, 23(11): 1294-1299.
[27] Lang B, Sun D Q, Xuan Z Z, et al. Hot cracking of resistance spot welded magnesium alloy[J]. ISIJ International, 2008, 48(1): 77-82.
[28] Yu Z H, Yan H G, Chen S J, et al. Method for welding highly crack susceptible magnesium alloy ZK60[J]. Science and Technology of Welding and Joining, 2010, 15(5): 354-360.
[29] 魏子淇, 刘正, 王志, 等. 钇对Mg-Zn-Y-Zr合金热裂敏感性影响[J]. 中国有色金属学报, 2018, 28(2): 233-240
Wei Ziqi, Liu Zheng, Wang Zhi, et al. Effects of Y on hot tearing susceptibility of Mg-Zn-Y-Zr alloys[J]. The Chinese Journal of Nonferrous Metals, 2018, 28(2): 233-240
[30] 伍迪灿, 王云峰, 杜文博, 等. Mg-xGd-1Er-0.5Zr合金热裂敏感性研究[J]. 中国有色金属学报, 2022, 32(2): 375-385
Wu Dichan, Wang Yunfeng, Du Wenbo, et al. Investigations on hot cracking susceptibility of Mg-xGd-1Er-0.5Zr alloys[J]. The Chinese Journal of Nonferrous Metals, 2022, 32(2): 375-385
[31] Flemings M C. Solidification processing[M]. New York: McGraw-Hill, 1974.
