MICROSTRUCTURE STUDIES OF POLYCRYSTALLINE REFRACTORY OXIDES

Abstract

Transverse bend strength and elastic modulus determinations made of fine-grained (1 to 2 micron), dense, pure Al2O3 and MgO specimens as a function of temperature (up to 1350 C) revealed values higher than those obtained by other investigators for these oxides in more porous form and of larger grain sizes. Studies of the grain growth kinetics of alumina and magnesia were conducted in order to obtain information to enable preparation of specimens with desired larger grain sizes for subsequent thermomechanical testing. Based on observations of the fracture modes exhibited by alumina and magnesia as a function of temperature, it was suggested that an elastic deformation or possible plastic flow in the so-called equicohesive temperature range may influence the mode of fracture. By analogy with findings in metals systems, it was hypothesized that the apparent transition from transgranular to intergranular fracture might occur below some critical stress rather than above some critical temperature.

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Document Details

Document Type
Technical Report
Publication Date
Feb 14, 1963
Accession Number
AD0296269

Entities

People

  • J. B. Mitchell
  • R. M. Spriggs
  • T. Vasilos

Tags

Communities of Interest

  • Air Platforms
  • Weapons Technologies

DTIC Thesaurus Topics

  • Creep
  • Critical Temperature
  • Elastic Properties
  • Electron Microscopes
  • Grain Growth
  • Grain Size
  • High Temperature
  • Materials
  • Materials Processing
  • Mechanical Properties
  • Mechanical Working
  • Mechanics
  • Modulus Of Elasticity
  • Physical Properties
  • Refractory Materials
  • Stresses
  • Surface Properties

Fields of Study

  • Materials science

Readers

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