Deformation behavior of Al/Cu in-situ metal-intermetallic laminates at low and high strain rates

Abstract

In this study, four Al-Cu based Metal-intermetallic laminated (MIL) composites were processed via diffusion bonding wherein in-situ reactions between Al and Cu produce various intermetallic phases. Varying amounts of intermetallic phases were obtained in the four MILs by control of processing parameters and their respective hardness and Young’s modulus values were obtained through nano-indentation. The MILs were compression tested at high and low strain rates in two test orientations: with the loading axis either parallel or perpendicular to the layers. It was found that the mechanical response of the MIL was anisotropic, with the samples tested in the parallel direction exhibiting higher strength than samples tested in the perpendicular direction. Samples in the parallel direction underwent early failure at strains as low at 4%, whereas in the perpendicular direction, the samples did not fail even at 22%. Moreover, the yield strength of the MIL was found to increase with the volume fraction of the intermetallic phase in both directions. Fractography of parallel samples after failure revealed long straight cracks along the middle of the intermetallic layer, which were aligned parallel to the compression axis. SEM of perpendicular tested samples from interrupted tests revealed multiple cracking of the intermetallic layer. In either orientation, cracks were not observed along with the metal-intermetallic interface. These observations are discussed in the context of isostrain, and isostress models and the role of the strength of the metal-intermetallic interface is highlighted. The effect of processing parameters on the type and amount of the various phases and on interface strength is also discussed.