Fracture mechanisms of Al-steel resistance spot welds: The role of intermetallic compound phases

• Published in: Engineering fracture mechanics 2024-11, Vol.311, p.110520, Article 110520
• Main Authors: Cho, Donghyuk, Ghassemi-Armaki, Hassan, Stoughton, Thomas B., Carlson, Blair E., Sung, Hyun-Min, Hwang, Jihoon, Legarth, Brian N., Whan Yoon, Jeong
• Format: Article
• Language: English
• Subjects: Cohesive zone model (CZM); Dissimilar welding; Ductile fracture; Heat affected zone (HAZ); Intermetallic compound (IMC)
• ISSN: 0013-7944
• DOI: 10.1016/j.engfracmech.2024.110520

•This study develops a fracture model for Al-steel Resistant Spot Weld.•Fracture mechanisms of Al-steel RSW are examined using a miniature weld performance test and in-situ micro DIC.•The sequence of fracture energy is a function of the Intermetallic Compound (IMC) phase.•The weld microstructure and metallographic characteristics are explored.•Finite element (FE) model analyzes the fracture mechanism with debonding behavior using the Cohesive Zone Model (CZM).•The Hosford-Mean fracture criterion successfully modeled the ductile fracture of the Al FZ and HAZ.•The weld performance and failure mode are substantially influenced by the IMC phase. This study explores the mechanical and metallographic characteristics of Al-Steel dissimilar resistance spot welds (RSW), with a particular focus on the intermetallic compound (IMC) phases and their impact on fracture mechanisms. Detailed metallographic analyses and novel miniature lap shear tests with in-situ Digital Image Correlation techniques were conducted to observe the crack propagation behavior. The findings revealed that the IMC phases significantly influence the crack path and fracture mechanisms, leading to variations in fracture energy. Specifically, three distinct IMC phases were identified at the weld interface, each exhibiting unique structural and mechanical properties, with corresponding fracture energies of approximately 0.03 kJ/m2, 1.1 kJ/m2, and 7.5 kJ/m2. These variations highlight the critical role of the IMC phase in determining the fracture behavior of the weld. The study further supported the development and validation of a finite element (FE) model, incorporating a Cohesive Zone Model to simulate debonding behavior and the Hosford-Mean fracture criterion to predict ductile fracture in the Al fusion zone, thereby successfully linking local material characteristics to mechanical properties.