Experimental assessment of the microstructure evolution and liquidus projection in the Mo-rich Mo–Si–B system

Abstract

The present work is focused on a deeper understanding of the microstructure evolution and the solidification reactions of alloys in the Mo-rich portion of the Mo–Si–B system. A number of 59 alloys were selected from the vicinity of the ternary eutectic point to carefully examine the Mo-rich liquidus surface. Therefore, the microstructural evolution of alloy compositions from different primary solidification areas was taken into account. Their solidification path was evaluated by employing the Alkemade theorem. The result is an experimentally based reassessment of the liquidus projection. Special attention had been payed to the Mo3Si primary solidification area and the MoSS–Mo5SiB2–Mo3Si ternary eutectic in the Mo-rich portion of the Mo–Si–B system. It could be shown that the primary Mo3Si phase region is larger as compared to present literature data. The eutectic point could be confirmed to contain 17 ± 1 at.% silicon and 7.5 ± 0.5 at.% boron. As the main outcome from the careful investigation of the solidification paths of numerous alloys a reconstructed liquidus projection is presented. Keywords: Intermetallics, Transition metal alloys and compounds, Microstructure, Scanning electron microscopy, Phase diagrams