Rakhi Km, Kang Seunggu, Shin Joonghan
Department of Future Convergence Engineering, Kongju National University, 1223-24 Cheonandaero, Seobuk-gu, Cheonan 31080, Republic of Korea.
Department of Mechanical and Automotive Engineering, Kongju National University, 1223-24 Cheonandaero, Seobuk-gu, Cheonan 31080, Republic of Korea.
Materials (Basel). 2023 Sep 27;16(19):6426. doi: 10.3390/ma16196426.
Laser welding, known for its distinctive advantages, has become significantly valuable in the automotive industry. However, in this context, the frequent occurrence of hot cracking necessitates further investigation into this phenomenon. This research aims to understand the hot-cracking mechanism in aluminum alloy (AA) 6061, welded using a laser beam in a lap joint setup. We used an array of material characterization methods to study the effects of processing parameters on the cracking susceptibility and to elucidate the hot-cracking mechanism. A laser power of 2000 W generated large hot cracks crossing the whole weld zone for all welding speed conditions. Our findings suggest that using a heat input of 30 J/mm significantly mitigates the likelihood of hot cracking. Furthermore, we observed that the concentrations of the alloying elements in the cracked region markedly surpassed the tolerable limits of some elements (silicon: 2.3 times, chromium: 8.1 times, and iron: 2.7 times, on average) in AA6061. The hot-cracking mechanism shows that the crack initiates from the weld root at the interface between the two welded plates and then extends along the columnar dendrite growth direction. Once the crack reaches the central region of the fusion zone, it veers upward, following the cooling direction in this area. Our comprehensive investigation indicates that the onset and propagation of hot cracks are influenced by a combination of factors, such as stress, strain, and the concentration of alloying elements within the intergranular region.
激光焊接以其独特优势而闻名，在汽车工业中已变得极具价值。然而，在此背景下，热裂纹的频繁出现使得有必要对这一现象进行进一步研究。本研究旨在了解在搭接接头设置中使用激光束焊接的6061铝合金（AA6061）中的热裂纹形成机制。我们使用了一系列材料表征方法来研究工艺参数对裂纹敏感性的影响，并阐明热裂纹形成机制。在所有焊接速度条件下，2000 W的激光功率都会产生贯穿整个焊接区域的大热裂纹。我们的研究结果表明，采用30 J/mm的热输入可显著降低热裂纹出现的可能性。此外，我们观察到，裂纹区域的合金元素浓度明显超过了AA6061中某些元素的耐受极限（硅：平均为2.3倍，铬：8.1倍，铁：2.7倍）。热裂纹形成机制表明，裂纹从两块焊接板之间界面处的焊缝根部开始，然后沿柱状枝晶生长方向扩展。一旦裂纹到达熔合区的中心区域，它会沿着该区域的冷却方向向上偏移。我们的全面研究表明，热裂纹的产生和扩展受到应力、应变以及晶间区域合金元素浓度等多种因素的综合影响。
