Core-shell precipitation and strengthening in an Al-Li-Yb ternary alloy

Core-shell precipitates offer the possibility of size focusing, coarsening resistance, and functionalizing precipitate sites while strengthening the material. In this study, the Al-Li-Yb ternary alloy was investigated over a range of compositions, combined with a two-step heat treatment process to obtain core-shell precipitates in this alloy. The core-shell precipitate obtained consists of a coherent Al3Yb core surrounded by an Al3Li shell, coherent with the Al matrix. The coherency was observed up to the core-shell precipitate size (∼40nm) explored in this study. Initially, the core displayed a bimodal size distribution; however, formation of the shell resulted in a significantly narrower size distribution. Further, the alloy with core-shell precipitate displayed improved mechanical property compared to homogenized and core-only versions of the alloy.