Tensile Strength and Fracture Morphology of Fe/Al Solid-State Bonding Interface Obtained by Forge Welding: Effect of Oxide Scale and Estimation of the Bond Strength of Each Phase
Tensile Strength and Fracture Morphology of Fe/Al Solid-State Bonding Interface Obtained by Forge Welding: Effect of Oxide Scale and Estimation of the Bond Strength of Each Phase
复制标题
DOI：
10.1007/s11661-022-06816-w
复制
发表时间：
2022-09-19
影响因子：
2.8
通讯作者：
Yamagishi, Hideki
中科院分区：
文献类型：
--
作者：
Yamagishi, Hideki
最近提出的高强度铁(Fe)/铝（Al）点锻接头，其反应层厚度在介观区域几乎不含金属间化合物（IMC），是一种界面抗拉强度未知的重叠片状材料。因此，为了测量界面的抗拉强度，通过将1 mm厚的SPCC板材材料与A2024T4挤压坯料夹在一起形成锻造构件，进行了直接拉伸试验。采用两种类型的SPCC，一种用SiC #1000磨料抛光，另一种涂覆约2 μ m厚的氧化皮，以探测污染层对强度的影响；均表现为粘结界面（BI）断裂，抗拉强度分别为250和175 MPa。这种焊接方法创造了一个新形成的表面，即使在存在氧化皮的情况下也可以用于相对高强度的粘合。断口表面观察和化学成分分析揭示了这些材料的断裂形态。磨粒材料的断裂界面大致分为Al基体和Fe/Al两相，氧化皮包覆材料的断裂界面除两相外，还分为Fe/Fe- o三相。只有Al基断口为韧性断口，其余断口均为相对脆性断口。采用二值化方法确定各断裂界面的面积分数，并根据在Fe/Al界面断裂对应应变下假设的复合规律估计各相的结合强度。据估计，一种良好的Fe/Al BI的拉伸强度势超过339mpa。测定焊前、焊后各材料的维氏硬度及组织变化；SPCC的硬度因加工硬化而显著提高，而A2024T4的硬度因热效应而降低。基于A2024构件焊接后强度的接头效率约为74%。
Recently proposed high-strength iron (Fe)/aluminum (Al) spot-forged joints, in which the thickness of the reaction layer is virtually intermetallic compound (IMC)-free in the mesoscopic region, are overlapping sheet materials for which the tensile strength of the interface is unknown. Thus, to measure the tensile strength of the interface, a direct tensile test was performed by sandwiching 1-mm-thick SPCC sheet material with A2024T4 extruded billets to create a forged member. Two types of SPCC were used, i.e., one polished with SiC #1000 abrasive and the other coated with approximately 2-mu m-thick oxide scale to probe the effect of the contaminant layer on the strength; both displayed bonded interface (BI) fracture, with tensile strengths of 250 and 175 MPa, respectively. This welding method, which creates a newly formed surface, can be used for relatively high-strength bonding even in the presence of oxide scale. Fracture surface observations and chemical composition analyses revealed the fracture morphology of these materials. The fracture interface was roughly divided into two phases, Al matrix and Fe/Al, for the abrasive material, and three phases, Fe/Fe-O in addition to the two phases for the oxide scale-coated material. Only the Al matrix fracture was a ductile fracture surface, while the others were relatively brittle fracture surfaces. The area fraction of each fracture interface was determined by binarization, and the bond strength of each of phase was estimated according to the composite law assumed at the strain corresponding to the Fe/Al interface fracture. The tensile strength potential of a sound Fe/Al BI was estimated to exceed 339 MPa. The Vickers hardness of each material before and after welding was determined along with the microstructural changes; the hardness of SPCC increased significantly due to work hardening, while that of A2024T4 decreased due to thermal effects. The joint efficiency based on the A2024 member strength after welding was approximately 74 pct.