In situ observations of compressive behaviour of aluminium foams by local tomography using high-resolution X-rays

Abstract

We have investigated the compressive behaviour of closed-cell aluminium foams using a high-resolution X-ray CT. The microstructures of cell walls or Plateau borders in the foams were visualized in 3D using the local tomography technique which is a high-resolution CT method to reconstruct a region of interest within a large sample. The shapes and the 3D distribution of micropores, particles, and regions of solute segregation in the foams are evaluated, comparing the cell walls with the Plateau borders. Under compressive loads, the damage behaviour of such microstructures has been observed using an in situ test rig. It is found that the microcracks were mainly initiated from the cell walls and the micropores with large diameters were also damaged. The crack initiation sites are classified from the results. In addition, a method for non-destructive characterization of elastic and plastic deformation in the foams, which is called a 3D microstructure gauge (MG) method, is presented. Thousands of micropores as markers on each load were automatically matched by the information of those volumes and surface areas. The local strain mapping by the MG indicates that the edges of the micropores with large diameters have large strain under compression and this is consistent with the crack analyses.

Acknowledgments

The synchrotron radiation experiments were performed at the BL20B2 and the BL47XU in the SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal Nos. 2003B0292-NM-np, 2003B0293-NM-np-Na, 2004A0356-CM-np, 2004A0358-CM-np-Na, and 2004B0457-NI-np). This work is supported by the New Energy and Industrial Technology Development Organization (NEDO) as Collaborative Research of Production and Fabrication Technology Development of Aluminium useful for Automobile Lightweighting.