Effect of hot extrusion, other constituents, and temperature on the strength and fracture of polycrystalline MgO

Journal Article · Wed Dec 01 00:00:00 EST 1993 · Journal of the American Ceramic Society; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1993.tb06602.x· OSTI ID:5494828

Rice, R W ^[1]

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1. W.R. Grace and Co.-Conn, Columbia, MD (United States)

Improved agreement was confirmed between the Petch intercept and single-crystal yield stresses at 22 C. Hot-extruded MgO crystal specimens stressed parallel with the resultant axial texture (1) gave the highest and least-scattered strength-grain size results at 22 C, (2) showed direct fractographic evidence of microplastic initiated fracture at 22 C and showed macroscopic yield at 1,315 and especially 1,540 C, and (3) fractured entirely via transgranular cleavage, except for intergranular failure initiation from one or a few grain boundary surfaces exposed on the subsequent fracture surface, mainly at 1,540 C. Hot-extruded, hot-pressed MgO billets gave comparable strength when fracture initiated transgranularly, but lower strength when fracture initiated from one or especially a few grain boundary surfaces exposed on the fracture. The extent and frequency of such boundary fracture increased with test temperature. While oxide additions of [<=] 5% or impurities in hot-pressed or hot-extruded MgO can make limited strength increases at larger grain sizes, those having limited solubility can limit strength at finer grain sizes, as can coarser surface finish. Overall, MgO strength is seen as a balance between flaw and microplastic controlled failure, with several parameters shifting the balance.

• OSTI ID: 5494828
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 76:12; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MAGNESIUM OXIDES
FABRICATION
GRAIN BOUNDARIES
MECHANICAL PROPERTIES
FRACTURE PROPERTIES
TENSILE PROPERTIES
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
MAGNESIUM COMPOUNDS
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
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