A study on the phase transformation of [formula omitted]-Al8Mn5 to LT-Al11Mn4 during solutionizing in AZ91 alloy.

• γ 2 -Al 8 Mn 5 phase transformed to LT -Al 11 Mn 4 phase due to uphill diffusion of Al. • Shell type structure developed where LT -Al 11 Mn 4 shell encapsulated γ 2 -Al 8 Mn 5 phase. • Higher volume of LT-Al 11 Mn 4 phase resulted in cracks in the shell. • Si, Fe and Mg content decreased in the LT-Al 11 Mn 4 during solutionizing. [Display omitted] γ 2 -Al 8 Mn 5 intermetallic particles are generally present in commercial Mg-Al-Zn alloys. The present study is concerned with the effect of solutionizing on the morphology and phase stability of the γ 2 -Al 8 Mn 5 particles in an as-cast AZ91 alloy. Analysis using energy dispersive spectroscopy (EDS) and electron back scattered diffraction (EBSD) in a scanning electron microscope (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT) suggests that solutionizing resulted in uphill diffusion of Al from the α-Mg matrix resulting in the phase transformation of γ 2 -Al 8 Mn 5 to Low Temperature (LT) -Al 11 Mn 4 phase. This leads to a shell type structure of LT-Al 11 Mn 4 encapsulating γ 2 -Al 8 Mn 5 and the formation of cracks in the LT-Al 11 Mn 4 phase. These can propagate during external loading, affecting the mechanical properties. Additionally, the content of Fe and Si decreased in the LT-Al 11 Mn 4 , which could potentially decrease locally the corrosion resistance. [ABSTRACT FROM AUTHOR]