Factors Determining the Morphology of Precipitation in Aluminum-Germanium and Aluminum-Silicon Alloys

摘要

HVEM in-situ studies of precipitation in Al-Si and Al-Ge alloys complemented by high resolution observations have provided a clear picture of the fundamental nucleation and growth processes. A model for the role of vacancies in precipitate growth was in general agreement with a dynamic sequence recording the loss of coherency during plate growth. High resolution images obtained on the NCEM's Atomic Resolution Microscope provided direct information of precipitate/matrix interface structure, internal precipitate structure and orientation relationships. Based on the observations, simple model nuclei for various morphologies are proposed. These suggest that variations in the absolute and local vacancy supersaturation give rise to the precipitate patterns observed. 19 refs., 9 figs., 1 tab. (ERA citation 12:047828)