Microstructural characterization of Mg-Al-Sr alloys

The microstructural details of fourteen Mg-Al-Sr alloys were investigated in the as-cast form by a combination of scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis and quantitative electron probe microanalysis (EPMA). The heat transfer method coupled with the DSC measurement has been utilized to determine the solidification curves of the alloys. The morphology and the chemical composition of the phases were characterized. The microstructure of the alloys is primarily dominated by (Mg) and (Al4Sr). In the present investigation, ternary solid solubility of three binary compounds extended into the ternary system has been reported and denoted as: (Al4Sr), (Mg17Sr2) and (Mg38Sr9). The (Al4Sr) phase is a substitutional solid solution represented by MgxAl4−xSr and has a plate-like structure. The maximum solubility of Al in Mg17Sr2 was found to be 21.3 at%. It was also observed that Mg38Sr9 dissolved 12.5 at% Al.