Compression Fatigue Properties of Closed-Cell Aluminum Alloy Foams Fabricated by Two-Step Foaming Method

Given the widespread applications of aluminum foams, they inevitably undergo cyclic compressive loading during service, and therefore, it is necessary to study their compression fatigue properties. In this work, closed-cell aluminum alloy foams (CAAF) are obtained by two-step foaming method with A356 as the matrix alloy. Pore structures and quasistatic compression properties of the foam are first analyzed. Subsequently, the effect of stress level and porosity on the compression-compression fatigue performances of CAAF is investigated based on quasistatic compression results. The results indicate a decrease in fatigue life of CAAF with increasing stress levels, with distinct trends observed in stages 2 and 3 of the epsilon-N curves for 80% porosity. Finally, deformation patterns and failure mechanism of internal porosity under compression-compression fatigue loading are analyzed through a combination of macroscopic characterization and finite element simulation. It is observed that CAAF exhibits two primary deformation modes, namely buckling deformation and shear deformation, under compression-fatigue loading. Crack initiation and propagation primarily occur at nonspherical cells and weaker cell struts with increasing strain.