Properties and Microstructures of High-Temperature Materials.
Abstract
This final technical report contains information on investigations whose aim was to study specific aspects of properties and microstructures of high-temperature materials. These investigations are: (1) fracture from controlled surface flaws in structural ceramics, (2) fractography of reaction-sintered silicon nitride, (3) oxidation behavior of titanium aluminides, and (4) creep behavior of titanium aluminide and titanium aluminide + 10 wt% Nb. The scientific basis and advantages and disadvantages of the microhardness indentation technique in producing controlled surface flaws and in studying the fracture behavior of structural ceramics are reviewed. The current applications of this technique--including fracture toughness determinations, subcritical-crack-growth measurements, and investigation of mixed-mode fracture--are discussed. An SEM fractography study has been carried out on bend bars of KBI and Norton NC-350 reaction-sintered silicon-nitride ceramics fractured at temperatures ranging from room temperature to 1500 C. The purpose of this study was to examine overall fracture features, identify and analyze the fracture-initiating critical flaws, and correlate these with four-point bend strength. The oxidation behavior of titanium aluminides is reported which includes the effect of temperature upon the oxidation of TiAl-base aluminides, the microstructural characterization of scale morphologies of both TiAl and Ti3Al, and the results of oxidation tests on alloys of TiAl and Ti3Al.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1978
- Accession Number
- ADA060386
Entities
People
- M. G. Mendiratta
- N. S. Choudhury