PSI - Issue 35

Varvara Romanova et al. / Procedia Structural Integrity 35 (2022) 196–202 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Nowadays, additive manufacturing (AM) techniques have particular importance in a wide range of modern industries providing appreciable advantages compared to the conventional subtractive methods. The powder-bed additive manufacturing process known as selective laser melting (SLM) offers an opportunity for constructing easily customizable complex-shaped metal parts along with reduction in a raw material consumption. Particularly, SLM is a promising AM technique in producing aluminum alloy parts. An AlSi10Mg alloy is commonly used for SLM due to its low melting point and a eutectic composition of Al and Si as reported by Li et al. (2021) and Kan et al. (2019). However, despite of the obvious competitive advantages, SLM spreading is still limited due to the number of unsolved scientific and industrial challenges. SLM is a process imposing directional heat deposition for a repeated powder melting. Extremely high heating and cooling rates during melting and solidification give rise to formation of a complex anisotropic structure throughout all scales as reported by Patakham et al. (2021). Thus, the presence of the hierarchical microstructure and texture specific for additive materials essentially complicates a full understanding of the material deformation behavior as written by Carrol et al. (2015). A number of experimental works have shown that the mechanical response of the aluminum alloys produced by SLM is highly inhomogeneous. For example, Liu et al. (2020) showed notable changes in maximum tensile stress, total elongation and stress hardening exponent of the aluminum specimens fabricated by laser powder bed fusion, loaded normal and parallel to the build direction. Tradowsky et al. (2016) reported that AlSi10Mg specimens loaded perpendicular to the build direction demonstrated improved tensile properties compared to those loaded parallel to the build direction. Ch et al. (2019) found the maximum strength had been exhibited by a vertically built AlSi10Mg sample while the lowest strength had been observed for a horizontally built sample. Sridharan et al. (2016) found that the specimens loaded parallel to the build direction had inferior properties as compared to those loaded perpendicular to the build direction. However, Prashanth et al. (2014) investigated SLM-built Al-12Si specimens loaded at different angles to the build direction and found no dependence of the yield stress on the specimen orientations. In this study, the crystal plasticity finite element (CPFE) simulations are performed in order to investigate the mechanical aspects of the grain-scale deformation behavior of an AlSi10Mg model under two types of uniaxial tension. The proposed numerical approach implies the simulation of the microstructure evolution of an AlSi10Mg alloy during SLM process and the subsequent mechanical analysis of its deformation behavior. The three-dimensional microstructural model is simulated by coupling the finite-difference (FD) calculation of heat transfer and the cellular automata (CA) modelling of solidification. The simulated grain structure (Fig. 1a) is well aligned with the experimental data (Fig. 1b). The detailed description of the simulation procedure is given by Mohebbi and Ploshikhin (2020).

Fig.1. Simulated grain-scale model of an SLM AlSi10Mg alloy (a); EBSD inverse pole figure mapping (Mohebbi and Ploshikhin, 2020) (b)

This paper presents the micromechanical analysis of the von Mises stress, plastic strain fields and deformation induced roughness patterns developing in the microstructural model of an AlSi10Mg model under two types of uniaxial tension.