A transmission electron microscopy investigation of defects in an Mg-Cu-Mn-Zn-Y damping alloy

A high number of dislocations have been observed in an as-cast high-damping Mg-3Cu-1Mn-2Zn-1Y (wt.%) alloy using transmission electron microscope (TEM). The majority of dislocations are distributed in parallel and uniform rows. Mg2Cu particles in the matrix are often found to be associated with a number of parallel dislocations. Twins containing stacking faults are also frequently observed. The formation of eutectic phases occurring during casting is followed by precipitation of secondary intermetallic phases in supersaturated α-Mg with alloying elements upon annealing. The observed defect structures provide useful experimental evidence supporting the previously proposed damping mechanism for Mg alloys.

► A large number of parallel dislocation rows support clearly on the dislocation mechanism of the Mg-Cu-Mn-Zn-Y alloy.
► Experimental evidence on the proposal that twins as another energy-dissipation source has been given.
► The parallel dislocations are found to be always associated with precipitates in the matrix.
► The as-cast alloy has large grain size, with major intermetalics in grain boundaries and sparsely distributed precipitates in matrix, which is supersaturated with Zn, Cu, and Mn.