Local mechanical properties and plasticity mechanisms in a Zn-Al eutectic alloy

Highlights: • Nanoindentation is used to investigate the deformation of individual phases in a complex microstructure. • High resolution strain partitioning in multiphase alloys is obtained by digital image correlation and electron microscopy. • A new non-rigid image registration method to study the local strain partitioning is proposed. In multiphase alloys, the mechanical properties are controlled by both the local properties of individual microstructural constituents, as well as the mutual effect of these constituents as an aggregate. To this end, we systematically studied the local mechanical properties and deformation mechanisms of the microstructural constituents in a ZnAl4Cu1Mg0.31 alloy using nanoindentation tests at room temperature (25 °C) and 85 °C. The obtained strain rate sensitivity and activation volume suggest dislocation-dominated deformation in the primary η-Zn phase and grain/phase boundary sliding in the eutectoid structures. Further, the strain partitioning between individual microstructural constituents and their roles on macroscopic deformation at 85 °C was investigated using quasi in-situ digital image correlation (DIC), supplemented with non-rigid image registration. The DIC measurements showed that eutectic and eutectoid colonies carry higher strain than the primary η-Zn phase grains. The presented approaches and results can therefore be used to design new Zn-Al alloys and also other multiphase alloys with improved mechanical properties.