Interface-correlated deformation behavior of a stainless steel-Al-Mg 3-ply composite

We investigate the influence of post-rolling heat treatment on the microstructural evolution and subsequent mechanical properties of a roll-bonded stainless steel (STS)-Al-Mg 3-ply clad sheet. Intermetallic compound (IMC) phases, gamma (Mg17Al12) and 3 (Mg2Al3), were generated at the interface between the constituent Mg and Al alloys. The thickness of the IMC layers increased to more than 10 mu m with increasing annealing time up to 3 h at 300 degrees C. Upon extending the annealing time to 12 h, the beta phase at the interface between Al and Mg hardened significantly, which was verified by investigating the local mechanical properties of the gamma and beta phases using nanoindentation. Furthermore, the mechanical properties of the three constituent alloys and the 3-ply clad sheets were systematically investigated by uniaxial tensile and flexural bending tests. Taking both tensile strength and elongation into account, the 3-ply sample annealed for 1 h at 300 degrees C exhibited acceptable overall mechanical properties. The mechanism for retarding interfacial delamination in the direction perpendicular to the transverse loading was also confirmed by observation from the side surfaces of the 3-point-bending-tested specimens. Abrupt longitudinal crack propagation was observed within the annealing-hardened beta phase, followed by the generation of short lateral cracks in the bending sample annealed for 3 h, indicating that the overannealing-induced brittleness of a specific IMC phase at the interface may be detrimental to overall mechanical properties of the roll-bonded 3-ply clad sheet adopted in this study. (C) 2012 Elsevier Inc. All rights reserved.