Failures analysis of in-situ Al–Mg2Si composites using actual microstructure based model

Abstract

In-situ Al–Mg2Si composites (0, 5, 10, 15, 20 wt% Mg2Si) were synthesized in an Al–Mg–Si system through gravity casting route. Influences of the Mg2Si addition (in terms of Mg and Si) on the mechanical properties, microstructural morphology, fracture behaviors, micro-mechanical response and failure initiation were systematically studied through experiments and mathematical modeling. Experimental results show that the primary Mg2Si formed in Al-10 wt% Mg2Si composite and the volume percentage and size of primary Mg2Si particles are increasing with an increase in Mg2Si concentration in the composite. The Mg2Si reinforcement significantly improves ultimate tensile strength (UTS), hardness and yield strength (YS) of the composite, but unwantedly the elongation decreased. Fracture surface analysis reveals that the composites have both the ductile and brittle mode of fracture and the amount of brittle fracture increased with an increase in reinforcing phase (Mg2Si) concentration. The fracture mode for the Mg2Si particles includes matrix yielding, decohesion, particle fracture. The deformation plasticity (Ramberg-Osgood) model was considered to investigate the micromechanical response under tension. Actual microstructure two-dimensional (2D) representative volume element (RVE) models have been developed to investigate the deformation and failure phenomenon of the composites. The FE analysis results have a great concurrence with the experimental one. It established that the composite's strength and failure initiation regions increased and the elongation decreased with an increase in Mg2Si concentration. It is noted that the eutectic Mg2Si morphology is the cause for failure initiation and then primary Mg2Si drive the final failure of the Al–Mg2Si composites.