Accession Number : AD0686874

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

Corporate Author : DEFENCE STANDARDS LABS MARIBYRNONG (AUSTRALIA)

Personal Author(s) : Southin,R. T. ; Jones, B. L.

Report Date : 30 SEP 1968

Pagination or Media Count : 8

Abstract : The morphology of the minor phase of directionally-solidified Pb/Ag, Bi/Ag and Sn/Ag3Sn 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 Bi/Ag and Sn/Ag3Sn 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 Pb/Ag 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)

Descriptors :   (*EUTECTICS, MICROSTRUCTURE), ELECTRON MICROSCOPY, LEAD ALLOYS, SILVER ALLOYS, BISMUTH ALLOYS, TIN ALLOYS, PHASE STUDIES, AUSTRALIA

Subject Categories : Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE