Ames Laboratory; Materials Science and Engineering
Ames Laboratory, Materials Science and Engineering
Phase selection and growth of materials far from equilibrium provides fertile ground for novel phases and morphologies since a multitude of different pathways may be energetically accessible. In this study, a complex metastable devitrification of Al60Sm11 (ε-phase) from its amorphous precursor is discovered using a combination of in-situ high-energy X-ray diffraction (HEXRD), providing insight into the average bulk behavior, and in-situ aberration corrected scanning transmission electron microscopy, revealing the atomic scale mechanisms of growth and their dynamics. We have found that non-equilibrium chemical partitioning disrupts the nominal planer growth by formation of nanoscale Al enriched regions inhomogeneously segregated at the ε/glass interface, to locally balance the compositionally dependent driving force and the associated diffusional burden imposed on its grain growth. These Al-rich regions form fcc-Al-rich nanocrystallites epitaxially with the ε-phase, modifying ε/glass interface mobility and creating a crenulated growth front. This new mechanism offers a pathway for fabricating alloy structures with nanoprecipitate dispersions through a meta-stable phase transition.
DOE Contract Number(s)
Department of Energy Subject Categories
36 MATERIALS SCIENCE
Iowa State University Digital Repository, Ames IA (United States)
Available for download on Thursday, November 14, 2019