Analysis of damage mechanisms in an AlSi10Fe0.7 model casting alloy based on a “digital twin”

Brittle phases have a major influence on the mechanical behavior of cast aluminum alloys. Among these, silicon precipitates are nearly omnipresent, as Si is a common alloying element. In secondary alloys, Fe -containing phases are generally unavoidable and tend to degrade the mechanical properties. This study investigates the interaction between the silicon phase and the failure-critical intermetallic phase β- Al 4.5 FeSi in the Al - Si - Fe phase system by a combined computational and experimental approach. A model alloy Al 10 Si 0.7 Fe was defined, which is composed of a large-grained Al -matrix, Si -precipitates and the plate-like β- Al 4.5 FeSi phase. The “digital twin” of a micro specimen cast with this model alloy was set up combining electron backscatter diffraction (EBSD) and computer tomography (μCT). EBSD provided the crystallographic orientation of the phases, while the μCT delivered the morphology and 3D distribution. Elastic-anisotropic, plastic-isotropic and crystal-plastic material models were used in the simulation. The study aimed at identifying “hot spots” in the microstructure where cracks might initiate under mechanical loading. The experimental tool was a deformation analysis via digital image correlation in the SEM (SEM-DIC). The experimental analysis is shown in (Ickler et al., 2024 [1]) in detail. In addition to the “real” tensile tests in the SEM, a “virtual” tensile test was performed with the “digital twin” using boundary conditions determined from the SEM-DIC experiment. The SEM-DIC results and simulations show that the deformation field is governed by the elastic incompatibility of the microstructural constituents. Crack initiation occurs because of the detachment of the Si +β- Al 4.5 FeSi phase boundary from the matrix (Ickler et al., 2024 [1]). The simulation provided a view in the subsurface domain, revealing that the deformation processes within the Al -matrix are closely linked to the orientation of the plate-like phases relative to the crystal orientation and load direction. When platelets are aligned with a suitable slip plane of the Al -matrix, significant shearing without rotational deformation along the inclusions can be observed even at low loads. When platelets are not aligned with a suitable slip plane, dislocations can accumulate at phase triple points, further increasing the stress concentration and leading to rotational deformation. The strain calculations from the simulation model at the surface exhibited excellent agreement with those obtained from the SEM-DIC experiment, thereby validating the simulation results. • A digital twin of a secondary Al Si casting was set up combining scanning electron microscopy (SEM) and computed tomography (μCT). • The deformation analysis combined digital image correlation in the SEM (SEM-DIC) and deformation simulations of a digital twin of a phase cluster. • Plastic-isotropic and crystal-plastic material models were compared. • The digital twin revealed that the deformation processes within the Al -matrix are closely linked to the orientation of the plate-like phases relative to the crystal orientation and load direction.