Martensite in die-cast magnesium alloy?

In this paper, the microstructures of a thin-wall die-cast commercial magnesium (Mg) alloy, aged at 200 °C for various times, were investigated using transmission electron microscopy. A martensite-like phase was observed. The crystal lattice parameters of this phase are a = 0.30948 nm, c = 0.50498 nm, and axial ratio c/a = 1.6314. Orientation relationship of the martensite-like phase and the parent has been determined as (0 0 0 1)product∥(1 0 1¯ 0)parent, and [0 0 0 1]product∥[1 0 1¯ 0]parent or [2 1¯ 1¯ 0]product||[2 1¯ 1¯ 3]parent. The driving force of the possible martensitic transformation (MT) might came from the residual microstructure stresses left during die-cast process.