Anisotropic dynamic compression response of a directionally-cast silver–copper eutectic alloy

At the eutectic composition, the silver–copper bi-phase system can be produced such that the Cu phase forms as discontinuous reinforcements within a silver matrix. The reinforcements and matrix have a 101 growth direction along the axial direction of the produced material. This work examines the compressive deformation response of four such unidirectional Ag–Cu materials with nominal, bilayer thickness of 3.6 μm, 2.2 μm, 1.1 μm and 500 nm. From the cast material, specimens were machined to investigate the material response parallel (0°) to the 〈101〉〈101〉 growth direction, 45° to the growth direction, and perpendicular (90°) to the growth direction. Specimens were loaded dynamically under compression using a split-Hopkinson pressure bar. The strength response of the unidirectional material was found to increase as the bilayer thickness decreased with the 0° orientation having the greatest strength followed by the 90° orientation then the 45° orientation. Deformation mechanisms were examined using postmortem microscopy. The orientation dependent strength and strain hardening are attributed to slip system orientations, deformation twinning, and the Ag–Cu interface structure.