Accession Number : AD0768840

Title :   The Effects of Microstructure on the Fracture Energy of Hot Pressed MgO,

Corporate Author : MASSACHUSETTS UNIV AMHERST SCHOOL OF ENGINEERING

Personal Author(s) : Kessler,J. B. ; Ritter,J. E. , Jr. ; Rice,R. W.

Report Date : JUL 1973

Pagination or Media Count : 29

Abstract : The work-of-fracture technique was used to investigate the effects of various microstructural parameters on the fracture energy of relatively dense, hot pressed MgO. Grain size, amount and location of porosity, and grain boundary precipitates were the parameters of major interest. The fracture energy measurements were found to be dependent on the microstructure and ranged from 0.47 to 2.7 x 10 to the 4th power ergs/sq cm. Grain boundary precipitates, found in the as hot-pressed samples with LiF additives, weakened intergranular bonding and caused the lowest fracture energies. Limited porosity (up to 1.0%) had only a small effect on the fracture energy when found at the grain boundaries, although this porosity did facilitate intergranular fracture. Porosity found within the grains appeared to promote a tearing between cleavage planes which in turn increased the fracture energy. The effect of grain size on fracture energy was not conclusive, although the percentage of transgranular fracture increased with grain size. These fracture energy values are compared to strength measurements and the limitations of the Griffith equation in explaining the results are discussed. (Author)

Descriptors :   (*MAGNESIUM OXIDES, FRACTURE(MECHANICS)), MICROSTRUCTURE, ENERGY, GRAIN SIZE, POROSITY, GRAIN BOUNDARIES

Subject Categories : Ceramics, Refractories and Glass

Distribution Statement : APPROVED FOR PUBLIC RELEASE