Aghajani Derazkola Hamed, García Eduardo, Eyvazian Arameh, Aberoumand Mohammad
Department of Mechanics, Design and Industrial Management, University of Deusto, 48007 Bilbao, Spain.
Department of Mechanical and Industrial Engineering, Qatar University, Doha 2713, Qatar.
Materials (Basel). 2021 Feb 14;14(4):908. doi: 10.3390/ma14040908.
In this study, dissimilar sheets including AA3003 aluminum and A441 AISI steel were welded via cooling-assisted friction stir welding (FSW). Three different cooling mediums including forced CO, forced water, and forced air were employed, and a non-cooled sample was processed to compare the cooling-assisted condition with the traditional FSW condition. The highest cooling rate belongs to CO and the lowest cooling rate belongs to the non-cooled sample as FSW. The best macrograph without any segregation at interface belongs to the water-cooled sample and the poorest joint with notable segregation belongs to the CO cooling FSW sample. The CO cooling FSW sample exhibits the smallest grain size due to the suppression of grain growth during dynamic recrystallization (DRX). The intermetallic compound (IMC) thickening was suppressed by a higher cooling rate in CO cooling sample and just Al-rich phase was formed in this joint. The lowest cooling rate in the FSW sample exhibits formation of the Fe rich phase. The IMC layers were thicker at the top of the weld due to closeness with the heat generation source. The water cooling sample exhibits the highest tensile strength due to proper mechanical bonding simultaneously with optimum IMC thickness to provide appropriate metallurgical bonding. Fractography observation indicates that there is a semi-ductile fracture in the water cooling sample and CO cooling sample exhibits more brittle fracture. Hardness evaluation reveals that the higher the cooling rate formed, the higher the hardness in stir zone, and hardness changes in the aluminum side were higher than the steel side.
在本研究中，通过冷却辅助搅拌摩擦焊（FSW）焊接了包括AA3003铝和A441 AISI钢在内的异种板材。采用了三种不同的冷却介质，即强制CO₂、强制水和强制空气，并加工了一个未冷却的样品，以将冷却辅助条件与传统搅拌摩擦焊条件进行比较。最高冷却速率属于CO₂，最低冷却速率属于未冷却的搅拌摩擦焊样品。界面无任何偏析的最佳宏观组织属于水冷样品，偏析明显的最差接头属于CO₂冷却搅拌摩擦焊样品。由于动态再结晶（DRX）过程中晶粒生长受到抑制，CO₂冷却搅拌摩擦焊样品的晶粒尺寸最小。在CO₂冷却样品中，较高的冷却速率抑制了金属间化合物（IMC）的增厚，并且在该接头中仅形成了富铝相。搅拌摩擦焊样品中最低的冷却速率表现出富铁相的形成。由于靠近发热源，焊缝顶部的IMC层较厚。水冷样品由于适当的机械结合以及最佳的IMC厚度以提供合适的冶金结合而表现出最高的拉伸强度。断口观察表明，水冷样品中存在半延性断裂，而CO₂冷却样品表现出更脆的断裂。硬度评估表明，形成的冷却速率越高，搅拌区的硬度越高，并且铝侧的硬度变化高于钢侧。
