A STUDY OF DEFORMATION AND FRACTURE OF THE EUTECTIC IN AN ADDITIVELY MANUFACTURED AL-SI COMPOSITE ALLOY

Abstract

The structure of AlSi12 alloy fabricated by wire-feed electron beam additive manufacturing was studied experimentally. A numerical study was performed to examine the thermomechanical behavior and fracture of a eutectic fragment at the scale of several microns. Boundary dynamic problems were solved under plane strain conditions. The composite structure of the eutectic system consisting of an aluminum matrix and silicon particles was taken into account explicitly in the calculations. Isotropic models of the thermoelastic-plastic matrix and elastic-brittle particles were implemented in ABAQUS/Explicit. Strains in the composite were calculated both with and without allowance for residual stresses caused by cooling after 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 stress of the matrix, while the ultimate fracture stress varies little. Favorable morphology of silicon particles was determined which prevents early fracture of the eutectic.