Constitutive and fracture behaviour of additively manufactured aluminium

Abstract

This paper presents a detailed experimental and numerical study into the constitutive and fracture behaviour of additively manufactured AlSi10Mg aluminium alloy produced by laser beam powder bed fusion (PBF-LB/M). A series of 26 coupons with various geometries (to achieve a range of stress states) and build directions ( θ = 0°, 45° and 90° relative to the layer direction, to investigate anisotropy) were additively manufactured and tested. The PBF-LB/M AlSi10Mg material showed mild constitutive anisotropy, with the highest Young’s modulus and proof strengths observed for the 0° coupons. For the case of smooth round bars, an appreciable discrepancy in engineering fracture strain was observed between repeated tests on the 90° coupons, with up to almost 60% differences, indicating potential variability in defect density. Complementary finite element models were developed to extract fracture strains and stress states. The analysis showed minor anisotropy in the fracture properties, with two outliers in the 90° coupons that exhibited considerably higher fracture strains than the 0° coupons, attributed to good interlayer adhesion and a reduced defect density near the critical cross-section. Two ductile fracture criteria, namely the Positive Stress Triaxiality-Lode Angle Parameter Interaction Model (PTLIM) and the Lode angle Modified Void Growth Model (LMVGM), were calibrated against the test data and shown to achieve comparable predictive capabilities.