Microstructure Studies of Polycrystalline Refractory Compounds

Abstract

Modifications were made in the press forging of three-inch Al2O3 hemispheres to eliminate cracking and surface reactions and yet maintain optical transmission resulting from crystallographic texture and high density. Further forgings of Si3N4 were conducted. Process modifications resulted in densities of over 98% with little or no edge cracking. Three additional Al2O3 powders were investigated in the continuing effort to identify and eliminate strength limiting flaws in hot pressed Al2O3. The predominant flaws found were large grain size zones and particulate inclusions. Fracture surface energies calculated from the indicated flaw size were much closer to those directly measured for single crystals than for polycrystalline material. Measurements of the solubility of carbon in Al2O3 were made after annealing in CO and CO2.

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Document Details

Document Type
Technical Report
Publication Date
Jun 01, 1974
Accession Number
AD0782647

Entities

People

  • Rowland M.
  • William H. Rhodes

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Crystal Structure
  • Crystals
  • Diffraction
  • Fabrication
  • Grain Boundaries
  • High Density
  • Hot Pressing
  • Manufacturing
  • Materials
  • Measurement
  • Mechanical Properties
  • Mechanical Working
  • Optical Properties
  • Press Forging
  • Strain Rate
  • Stresses
  • Surface Energy

Fields of Study

  • Materials science

Readers

  • Materials Science (Mechanical Engineering).
  • Materials Science and Engineering.
  • Metallurgy