A Study of Deformation and Fracture of the Eutectic in an Additively Manufactured Al-Si Composite Alloy

Experimental and numerical studies were conducted on AlSi12 alloy fabricated by wire-feed electron beam additive manufacturing to examine the structure, thermomechanical behavior and fracture of a eutectic microvolume at the scale of several microns. Dynamic boundary value problems were solved under plane strain conditions. The composite structure of the eutectic phase consisting of an aluminum matrix and silicon particles was taken into account explicitly in the calculations. Isotropic models of the thermoelastoplastic matrix and elastic-brittle particles were implemented in ABAQUS/Explicit. Composite deformation was calculated both with and without allowance for residual stresses caused by cooling of the composite after its fabrication. It was shown that after the cooling of the eutectic, silicon particles are compressed, and the aluminum matrix is under both bulk compressive and tensile as well as under pure shear stresses. It was found that residual stresses play a negative role at the stages of intense deformation of the composite. The fracture strain of the eutectic strongly depends on the yield point of the matrix, while the ultimate fracture stress varies but only slightly. Favorable morphology of silicon particles was determined which prevents early fracture of the eutectic.