Synthesis & Fundamental Studies of Bulk Metallic Systems Based on Unusual Microstructures
Abstract
We have performed integrative studies of thermal and mechanical effects on the synthesis and properties of bulk titanium-based alloys with nanoscale morphological structures. Alloys are examined by calorimetry, mechanical-property testing, and x-ray and electron diffraction including high-resolution analytical microscopy. New titanium alloys with unusual structural and physical properties are found and preliminary studies of various phase formation pathways have begun, several key results are reported: (1) A series of high-order beta-phase Ti-alloys obtained as ingots are found to undergo nanocrystallization and amorphization upon annealing. The premise for solid-state vitrification and nanocrystallization (SSVN) is studied in light of the free energy difference between the BETA phase and amorphous phase. (2) The study of SSVN is generalized to include SSV via the mechanical pathway. The easy amorphization via mechanical milling is found to correlate strongly with SSVN via annealing, which provides the basis for future study of "inverse melting" in our Ti-alloys. (3) Nanoscale spatial resolution of spinodal decomposition in high-order beta Ti-alloys during isothermal annealing is studied using high resolution analytical electron microscopy. (4) The study of SSVN has also resulted in a new class of high-strength beta alloys with good ductility obtained in 85 at.% Ti-alloys with uniformly dispersed nanocrystalline alpha-phase particles.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 15, 1998
- Accession Number
- ADA358301
Entities
People
- G. J. Shiflet
- S. J. Poon
Organizations
- University of Virginia