Fracture Response of Additively Manufactured Aluminum Alloys: Effects of Loading Rate and Build Orientation

Abstract

AbstractAluminum alloys are the go-to alloys for numerous lightweight applications in automotive and aerospace industries. Excellent specific stiffness, specific strength, resistance to corrosion, and good machinability are some of the characteristics which make them highly desirable to these industries. The potential for aluminum alloys to be used in safety critical applications have expanded over the last few years because of the introduction of additive manufacturing (AM). AM, however, introduces uncertainties into the material which could affect the mechanical properties of parts in general and fracture properties in particular relative to conventionally produced ones. In this work, a popular AM aluminum alloy, AlSi10Mg, and a new AM aluminum alloy, AlF357, were fabricated using Laser Beam Powder Bed Fusion (LB-PBF) approach to evaluate quasi-static and dynamic fracture responses. Four build orientations – horizontal, vertical, flat, and diagonal – were assessed. An Instron mechanical tester and a Kolsky bar apparatus were used separately to carry out quasi-static and dynamic loading experiments, respectively, on notched samples. The local in-plane surface displacements near the crack tip were measured using Digital Image Correlation (DIC) to evaluate the fracture parameters directly. A hybrid experimental-numerical approach that combines DIC measurements and finite element analysis was implemented to extract critical energy release rate and crack growth resistance behaviors. The performance of the two alloys at two disparate strain rates is compared. The effect of the build orientation in these two aluminum alloys is also studied and the respective fracture properties are quantified.KeywordsAluminum alloyAdditive manufacturingFracture mechanicsHigh strain-rate fractureDigital Image Correlation