Determining Compositional Variation in Silicon-Metal Alloys by Parsing SEM/EDS Hyperspectral Images

High-temperature differential scanning calorimetry was used to understand the thermal properties of Si-rich metal–silicon alloys. Insoluble metals (A and B) were found to produce an alloy with discrete ASi2 and BSi2 dispersed phases. In contrast, metals that form a solid solution result in a dispersed phase that has a composition of AxB1−xSi2, where x varies continuously across each inclusion. This complex composition distribution is putatively caused by differences in the solidification temperatures of ASi2 versus BSi2. Though this behavior was observed for several different combinations of metals, we focus here specifically on the Cr/V/Si system. To better understand the range and most probable element concentrations in the dispersed silicide domains, a method was devised to generate histograms of their Cr and V concentrations from energy-dispersive X-ray spectroscopy hyperspectral images. Varying the Cr/V/Si ratio was found to change the shape of the element histograms, indicating that the distribution of silicide compositions that form is controlled by the input composition. Adding aluminum was found to result in dispersed phases that had a single composition rather than a range of Cr and V concentrations. This demonstrates that aluminum can be an effective additive for altering solidification kinetics in silicon alloys.