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) 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.