Accession Number:

AD0686874

Title:

THE MICROMORPHOLOGY OF HIGH VOLUME-RATIO EUTECTICS: A SCANNING ELECTRON MICROSCOPE STUDY,

Descriptive Note:

Corporate Author:

DEFENCE STANDARDS LABS MARIBYRNONG (AUSTRALIA)

Personal Author(s):

Report Date:

1968-09-30

Pagination or Media Count:

8.0

Abstract:

The morphology of the minor phase of directionally-solidified PbAg, BiAg and SnAg3Sn eutectic alloys were studied, over a large range of growth rates, by examination in a scanning electron microscope. At intermediate growth rates the Ag-phase is shown in all cases to grow as parallel branching ribbons. Two-dimensional microsections of these specimens show the broken lamellar appearance because branching takes place only in the plane of the parent ribbon. In the BiAg and SnAg3Sn alloys, the ribbons grow along preferred crystallographic directions and therefore branching takes place at fixed angles increase in the growth rate leads simply to a refinement in the scale of the structure. No preferred growth direction is indicated, however, in the PbAg alloy and, in this case, increase in the growth rate leads to a gradual breakdown to the so-called acicular structure. The Ag-phase is shown here to consist not of needles but of wide non-parallel ribbons with fringed edges. Author

Subject Categories:

  • Properties of Metals and Alloys

Distribution Statement:

APPROVED FOR PUBLIC RELEASE