Accession Number : ADA328291

Title :   Materials Processing and Microstructure Control in High Temperature Ordered Intermetallics.

Descriptive Note : Final progress rept. 15 Aug 90-31 Jul 94,

Corporate Author : WISCONSIN UNIV-MADISON DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Perepezko, J. H.

PDF Url : ADA328291

Report Date : 16 JUN 1997

Pagination or Media Count : 74

Abstract : In the development of high temperature intermetallic systems for structural applications a crucial issue is the formulation of materials processing strategies in order to achieve controlled microstructures that are designed to provide for the required mechanical performance. In the current research an integrated approach that couples processing with microstructure control as guided by the operative phase equilibria has been used to identify several promising intermetallic alloys. The experimental efforts have focused on three areas involving a coordination of phase equilibria information with solidification processing and a fourth area dealing with reaction analysis during composite processing. In the Ti-Al-Nb ternary system new information on the phase stability at elevated temperature has allowed for the design of an aligned multiphase microstructure. A gradient recrystallization treatment has been devised to yield a unidirectional (alpha sub 2+ gamma) microstructure. In the Ti-Mo system reaction pathways have been identified that allow for the formation of ductile phase dispersoids in gamma-TiA1 as part of stable two-phase microstructures. In the second area the selective alloying of MoSi2 has been examined to address low temperature ductility problems. The third area of effort involved the processing of alloys containing NbCr2, Laves phase together with a BCC phase. A new approach to the analysis of solubility in Laves phases has been devised based on solute atom size factor. In Nb-Cr-Mo alloys a new design including a strengthened BCC phase together with the Laves phase has been identified. In the final area a new analysis relating to the effectiveness of diffusion barrier coatings has been formulated to examine Ti based metal matrix composites with Al2O3 reinforcements.

Descriptors :   *THERMAL STABILITY, *INTERMETALLIC COMPOUNDS, MECHANICAL PROPERTIES, MICROSTRUCTURE, METAL MATRIX COMPOSITES, PHASE STUDIES, RELIABILITY, ALUMINUM OXIDES, TITANIUM ALUMINIDE, DUCTILITY, RECRYSTALLIZATION, MOLYBDENUM ALLOYS, BARRIER COATINGS, DIFFUSION COATINGS.

Subject Categories : Metallurgy and Metallography
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE