Effect of glass additions on the indentation-strength behavior of alumina

O`Donnell, H L; Readey, M J; Kovar, D

doi:10.1111/j.1151-2916.1995.tb08405.x

Title: Effect of glass additions on the indentation-strength behavior of alumina

Full Record
Other Related Research

Abstract

The effect of small calcium aluminosilicate (CAS) glass the microstructure and flaw tolerance of alumina ceramics is investigated, and the results compared to a high-purity alumina. The high-purity alumina specimens were dense with microstructures consisting of a uniform grain size distribution and equiaxed grain morphology. Additions of only 1 wt% glass phase resulted in a bimodal grain size distribution containing large, elongated grains within a fine-grain matrix. Indentation-strength tests indicated enhanced flaw tolerance with the bimodal microstructure, even though both materials had nominally the same average grain size. The strength of unindented specimens was also observed to decrease with glass additions. Observations of crack paths show a greater propensity for bridging in the glass-containing alumina due to the presence of coarse, elongated grains and perhaps a lower grain boundary toughness. However, crack extension occurs transgranularly when the size of the coarsest grains becomes too large. This suggests that an optimum in flaw tolerance will be achieved with an elongated grain morphology and in mediate grain size.

Authors:

O`Donnell, H L; Readey, M J; Kovar, D ^[1]

Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Materials Science and Engineering

Publication Date:: Sat Apr 01 00:00:00 EST 1995

Research Org.:: Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)

OSTI Identifier:: 82579

DOE Contract Number:: AC04-94AL85000

Resource Type:: Journal Article

Journal Name:: Journal of the American Ceramic Society

Additional Journal Information:: Journal Volume: 78; Journal Issue: 4; Other Information: PBD: Apr 1995

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; ALUMINIUM OXIDES; MICROSTRUCTURE; FRACTURE PROPERTIES; CALCIUM SILICATES; ALUMINIUM SILICATES; GLASS; DEFECTS; GRAIN SIZE; MORPHOLOGY; CRACK PROPAGATION; GRAIN BOUNDARIES

Citation Formats


                    O`Donnell, H L, Readey, M J, and Kovar, D. Effect of glass additions on the indentation-strength behavior of alumina.  United States: N. p., 1995. 
        Web.  doi:10.1111/j.1151-2916.1995.tb08405.x.

Copy to clipboard


                    O`Donnell, H L, Readey, M J, & Kovar, D. Effect of glass additions on the indentation-strength behavior of alumina.  United States.  https://doi.org/10.1111/j.1151-2916.1995.tb08405.x

Copy to clipboard


                    O`Donnell, H L, Readey, M J, and Kovar, D. 1995.  
        "Effect of glass additions on the indentation-strength behavior of alumina".  United States.  https://doi.org/10.1111/j.1151-2916.1995.tb08405.x.

Copy to clipboard


                    
@article{osti_82579,

  title        = {Effect of glass additions on the indentation-strength behavior of alumina},

  author       = {O`Donnell, H L and Readey, M J and Kovar, D},

  abstractNote = {The effect of small calcium aluminosilicate (CAS) glass the microstructure and flaw tolerance of alumina ceramics is investigated, and the results compared to a high-purity alumina. The high-purity alumina specimens were dense with microstructures consisting of a uniform grain size distribution and equiaxed grain morphology. Additions of only 1 wt% glass phase resulted in a bimodal grain size distribution containing large, elongated grains within a fine-grain matrix. Indentation-strength tests indicated enhanced flaw tolerance with the bimodal microstructure, even though both materials had nominally the same average grain size. The strength of unindented specimens was also observed to decrease with glass additions. Observations of crack paths show a greater propensity for bridging in the glass-containing alumina due to the presence of coarse, elongated grains and perhaps a lower grain boundary toughness. However, crack extension occurs transgranularly when the size of the coarsest grains becomes too large. This suggests that an optimum in flaw tolerance will be achieved with an elongated grain morphology and in mediate grain size.},

  doi          = {10.1111/j.1151-2916.1995.tb08405.x},

  url          = {https://www.osti.gov/biblio/82579},
  journal      = {Journal of the American Ceramic Society},
number       = 4,

  volume       = 78,

  place        = {United States},

  year         = {Sat Apr 01 00:00:00 EST 1995},

  month        = {Sat Apr 01 00:00:00 EST 1995}

}

Copy to clipboard

Journal Article:

https://doi.org/10.1111/j.1151-2916.1995.tb08405.x

Other availability

Find in Google Scholar

Search WorldCat to find libraries that may hold this journal

Save / Share:

Export Metadata

Save to My Library

Similar records in OSTI.GOV collections:

Grain size distributions and strength variability of high-purity alumina

Journal Article Kovar, D; Readey, M - Journal of the American Ceramic Society

Two batches of high-purity, alumina ceramics having an equiaxed grain morphology were manufactured with a mean grain size of approximately 10 {micro}m. A low-temperature heat treatment performed prior to sintering on one batch of specimens resulted in a narrow grain size distribution. The other batch of specimens was fired in a conventional manner and exhibited a broader grain size distribution. Mechanical tests performed on these specimens indicated little difference in the flaw tolerance of T-curve behavior of the aluminas, despite the presence of coarser grains in the conventionally fired alumina. Observations of cracks in these high-purity aluminas revealed that largemore »« less
https://doi.org/10.1111/j.1151-2916.1996.tb08121.x
The effect of grain shape on strength variability of alumina ceramics

Conference Readey, M

Fine-grained and coarse-grained aluminas containing either equiaxed or elongated grain structures were fabricated from commercial-purity and high-purity alumina powders. Compared to the high-purity aluminas, the commercial-purity aluminas having a coarse grain size and elongated grain structures exhibited significantly more pronounced flaw tolerance and T-curve behavior. T-curve behavior determined from indentation strength tests suggested that only the coarse- grained, elongated-grain alumina had a T-curve sufficient to cause stable crack extension prior to failure, a requirement for any observable improvement in reliability. In the high-purity aluminas as well as the fine-grained commercial-purity aluminas, however, it is likely that little or no stablemore »« less
Full Text Available
Crack stability and strength variability in alumina ceramics with rising toughness-curve behavior

Journal Article Kovar, D; Bennison, S; Readey, M - Acta Materialia

Aluminas with four distinct microstructures have been fabricated to investigate the influence of grain size and grain morphology on strength variability. The four microstructures comprise two grain size scales and are characterized as either equiaxed with a narrow size distribution or elongate with a higher aspect ratio and a broader size distribution. Indentation-strength tests indicate that only the coarse-grain, elongate microstructure exhibits a strong rising toughness-curve (T-curve or R-curve). Furthermore, in situ measurements demonstrate that the coarse-grain, elongate microstructure is the only one that displays significant stable crack extension from annealed indentation flaws free of contact-induced residual stress. Strength testsmore »« less
https://doi.org/10.1016/S1359-6454(99)00350-X
Role of grain size in strength variability of alumina

Journal Article Kovar, D; Readey, M - Journal of the American Ceramic Society; (United States)

Relationships between grain size and strength variability in alumina were investigated. Results are presented for an ultra-high-purity alumina with a narrow grain size distribution and an equiaxed grain morphology at three grain sizes ranging from 5 to 27 [mu]m. Vickers indentations are used to introduce controlled flaws into the specimens. It is found that increasing the grain size leads to enhanced flaw tolerance owing to a rising R-curve. However, contrary to recent theoretical predictions, no reduction in strength variability is found with increasing grain size. It is proposed that increasing variability in local fracture toughness with grain size offsets anymore »« less
https://doi.org/10.1111/j.1151-2916.1994.tb07073.x
Role of microstructure in Hertzian contact damage in silicon nitride. 1: Mechanical characterization

Journal Article Lee, S; Wuttiphan, S; Lawn, B - Journal of the American Ceramic Society

In this Part 1 of a two-part study of Hertzian indentation in silicon nitride the authors characterize irreversible contact damage as a function of microstructure. Three controlled silicon nitride microstructures are examined, representing a progression toward greater long-crack toughness: fine (F), bimodal with predominantly equiaxed {alpha} grains; medium (M), bimodal with mostly {beta} grains of intermediate size; and coarse (C), with almost exclusively elongated {beta} grains. An effect of increasing the microstructural heterogeneity in this sequence is to suppress ring cracking around the indenter, ultimately to a degree beyond that expected from increased toughness alone. Along with the crack suppressionmore »« less
https://doi.org/10.1111/j.1151-2916.1997.tb03129.x

Similar Records