High temperature in-situ 3D monitor of microstructure evolution and heat transfer performance of metal foam

Metal foams with excellent mechanical properties and low effective thermal conductivity (ETC) are widely used in high-temperature components. The 3D microstructure evolution under high-temperature loading is complex. The deformation mode and ETC at high temperature of metal foams are determined by the microstructure at different stress and the parent material properties. In this paper, high-temperature in-situ micro X-ray computed tomography (μ-CT) compressive test was performed to monitor the 3D microstructure evolution and failure mechanism of closed-cell Al foams at 300 ℃. High-fidelity material twin models were then generated from the in-situ μ-CT scans under various high-temperature loadings to calculate the corresponding ETC of the foams. The effects of the applied strain and corresponding 3D microstructure on the ETC were discussed based on experimental and simulation results. The results reveal that the 3D porosity and ETC evolution of foam compressed at 300 °C are bilinear. A compressive strain of 30 % was identified as a critical strain, beyond which both porosity and ETC change dramatically with increasing strain. Finally, a theoretical model based on the Kelvin tetrakaidecahedron was developed to reveal the effect of microstructure evolution caused by compressive strain on the ETC of foams.