Low-cycle fatigue behavior of friction stir welded joint of additively manufactured and cast AlSi10Mg: A combined experimental and multiscale modeling approach

Welding of a part produced by the laser-based powder bed fusion (PBF-LB/M) additive manufacturing process to a conventionally manufactured (CM) part is being widely investigated to overcome the limitation of part size that can currently be fabricated using a PBF-LB/M machine, and to produce a larger, more cost-efficient structure. Such a hybrid welded joint contains large variations in microstructural features along its length, which strongly affect the joint's fatigue behavior and lifetime. The objective of the present study is to investigate the effect of microstructural aspects of each region on its and the overall joint’s cyclic behavior with the help of a combined experiment and multiscale modeling approach. In the present study, a friction stir-welded joint of AlSi10Mg produced by PBF-LB/M and cast is used. A micromechanical model is applied to dual-phase synthetic microstructures to predict the cyclic behavior of each joint region, followed by a macroscopic model to predict the overall fatigue properties of the entire joint. The simulation results and observations align well with the experimental investigations. The simulated local stress-strain distribution reveals how strength and distribution of the phases, along with crystallographic aspects, influence the fatigue behavior of each welded region. The macro simulation also accurately predicted the joint's fatigue behavior over multiple cycles and the potential fatigue crack initiation site. Therefore, the method used in the present study can reliably predict the mechanical behavior of welded joints of AM components and thereby accelerate the application of AM welded joints in industrial applications.