Accession Number : ADA271491

Title :   Strengthening of NiAl Matrix Composites.

Descriptive Note : Final rept. Oct 90-Sep 93,

Corporate Author : MARYLAND UNIV COLLEGE PARK METALLURGICAL MATERIALS LAB

Personal Author(s) : Arsenault, Richard J.

Report Date : OCT 1993

Pagination or Media Count : 32

Abstract : It has finally been concluded that none of the existing theories could account for the observed high temperature strengthening, nor could the models or theories that we considered. This led to the prediction that the strengthening at high temperatures was the result of an increase in strength in the intermediate temperature range where the yield stress is relatively independent of temperature. We believe that the increase in stress is due to an increase in the athermal component of the yield stress, a component of the yield stress which is not overcome by thermal fluctuations. A TEM investigation was undertaken of continuous filament Al2O3/NiAl composites to determine if dislocations were generated as a result of the relaxation of the thermal residual stress. The data indicates that dislocation generation did indeed occur and there is a possibility that dislocation generation also occurs in shot fiber Al2O3/NiAl composites. This data may produce an interesting paradox since in Al2O3/NiAl composites, as the size of the reinforcement gets larger the dislocation density increases, but in SiC/Al composites, as the size of the SiC increases the dislocation density decreases at a constant volume fraction. Intermetallic Matrix Composites, TiB2/NiAl

Descriptors :   *METAL MATRIX COMPOSITES, *NICKEL, *ALUMINUM, *INTERMETALLIC COMPOUNDS, *TITANIUM BORIDE, CONSTANTS, DENSITY, DISLOCATIONS, FIBERS, FILAMENTS, HIGH TEMPERATURE, MODELS, PREDICTIONS, RELAXATION, RESIDUAL STRESS, VOLUME, ALLOYS, STRENGTH(MECHANICS), OXIDES, SILICON CARBIDES, COMPOSITE MATERIALS.

Subject Categories : Laminates and Composite Materials
      Mechanics
      Inorganic Chemistry
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE