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, γ (Mg17Al12) and β (Mg2Al3), were generated at the interface between the constituent Mg and Al alloys. The thickness of the IMC layers increased to more than 10 μm with increasing annealing time up to 3 h at 300 °C. Upon extending the annealing time to 12 h, the β phase at the interface between Al and Mg hardened significantly, which was verified by investigating the local mechanical properties of the γ and β 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 °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 β 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.