Micromechanical modeling of the low-cycle fatigue behavior of additively manufactured AlSi10Mg

Abstract

Factors such as high degrees of design freedom and flexibility in the production process contribute to a continued interest in the additive manufacturing (AM) process in industrial and academic research. The AM-processed components are widely used in industries; however, their use for production of parts under cyclic loading is still limited due to a significant variance in the cyclic behavior and the effect of the AM-associated defects, like porosity or unmelted powder, on the fatigue resistance. Micromechanical modeling approaches can be used to understand the relationship between the microstructure and the cyclic properties of the AM-processed material and thus expedite its employment in safety-critical applications. By using experiments and microstructure-sensitive models, this study aims to examine and to predict the low-cycle fatigue (LCF) behavior of AlSi10Mg parts produced by laser-based powder bed fusion in both the as-built and the direct-aged condition. Fatigue testing reveals higher stress amplitudes and cyclic hardening capabilities for the as-built condition. Direct-aged specimens demonstrate a higher number of cycles to failure at the highest strain amplitude, albeit at lower stress amplitudes when compared to the as-built condition. Both conditions show significant mean stress relaxation during LCF testing at a load ratio of R = 0. The applied modeling framework consists of a J2-plasticity model for the Si-rich phase and a crystal plasticity model for the Al phase. This hybrid model accurately predicts the LCF behavior under various strain amplitudes and ratios for both the as-built and direct-aged conditions of the AlSi10Mg.