Relation between Tensile Strut and Compressive Foam Deformation Behaviour: Failure Mechanisms and the Influence of Dendritic Versus Globular Grain Structure in an AlSi7Mg0.3 (A356) Precision‐Cast Open‐Cell Foam

Abstract

Open‐cell aluminum foams are gaining importance for the design of lightweight structures and as electrodes in lithium‐ion batteries. AlSi7Mg0.3 foams were produced by a modified investment‐casting process. By tuning the mold temperature, a change from the usual nearly monocrystalline dendritic to a polycrystalline globular grain structure was achieved. Tension and compression tests on single struts and foam specimens, respectively, were combined with digital image correlation, scanning electron microscopy, and phase‐contrast enhanced micro‐computed tomography in a synchrotron facility to correlate the mechanical properties and the failure mechanisms with the microstructure. The “globular” foams exhibited a lower strength and a less pronounced subsequent stress drop than the “dendritic” foams, and the deformation mechanism changed from shear‐band dominated failure to a layer‐by‐layer collapse, because of the lower strength and higher ductility of the “globular” struts. The “dendritic” struts have a more homogeneous microstructure, while the “globular” struts often contain silicon agglomerates in their central region. Accordingly, the latter struts exhibit a higher degree of scatter for the fracture strain. Thus, the arrangement of the silicon particles and the eutectic determines the mechanical properties on the strut level and thereby the failure behavior on the foam level.This article is protected by copyright. All rights reserved.