Accession Number : AD0809320

Title :   STRUCTURAL AND SOLIDIFICATION BEHAVIOR IN UNDERCOOLED GA-IN EUTECTIC ALLOY.

Descriptive Note : Final technical rept.,

Corporate Author : THAYER SCHOOL OF ENGINEERING HANOVER NH

Personal Author(s) : Lo, John M. ; Colligan, George A.

Report Date : 20 FEB 1967

Pagination or Media Count : 83

Abstract : Bulk samples of eutectic Ga-24.5% In have been undercooled to investigate structural and solidification behavior. Thermal measurements on cooling and heating cycles have disclosed four principal modes of metastable phase transformations. On cooling below the eutectic temperature, the terminal In-rich phase precipitates. Nucleation and growth from the remaining Ga-enriched undercooled liquid follow the sequence: Ga I-In for mode A; metastable Ga3In2, and GaI-In for mode B; metastable Ga II-Ga3In2, and GaI-In for mode C; metastable Ga II-In, and Ga I-In for mode D. These phase transitions conform to Ostwald's rule of reaction in successive steps of free energy reduction from the unstable liquid to the most stable solid phases Ga I-In. Heterogeneous nucleation involving the phases exhibit increasing catalytic potency as nucleating agents in the order: In, Ga3In2, Ga II, and Ga I. Structural changes during the transformation process have been followed by electrical resistivity measurements. Upon undercooling, a significant continuous negative departure from linear temperature dependence occurs as a result of In precipitation.

Descriptors :   (*GALLIUM ALLOYS, CRYSTALLIZATION), (*SUPERCOOLING, INDIUM ALLOYS), EUTECTICS, X RAY DIFFRACTION, NUCLEATION, ELECTRICAL RESISTANCE, TRANSFORMATIONS, REDUCTION, STRUCTURAL PROPERTIES, ANISOTROPY, MICROSTRUCTURE, THERMAL PROPERTIES, CATALYSIS, CATALYSTS, CRYSTAL STRUCTURE, METALLOGRAPHY.

Subject Categories : Properties of Metals and Alloys
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE