Degree Type

Dissertation

Date of Award

1980

Degree Name

Doctor of Philosophy

Department

Materials Science and Engineering

Abstract

The Young's modulus of polycrystalline Al(,2)O(,3), Gd(,2)O(,3), and MgTi(,2)O(,5) was measured as a function of temperature. Hysteresis between heating and cooling data was observed for all of the Gd(,2)O(,3) and MgTi(,2)O(,5) specimens, and for the Al(,2)O(,3) specimens having the largest grain size. The observed hysteresis is attributed to the opening of microcracks during cooling and to crack closure during heating;A theoretical model was developed to describe T(,MB), the temperature at which microcracking begins, as a function of grain size. The Cleveland-Bradt equation for critical grain size was also extended so that it could be compared to the model developed in this study. For each of the three materials studied, the slope of T(,MB) versus grain size agreed relatively well with that predicted by the model, to within a multiplicative constant of about 1.7162. The extended Cleveland-Bradt equation fit the data less well;A graphical method of predicting critical grain size was also demonstrated;('1)This research was supported by the Engineering Research Institute of Iowa State University through funds provided by the National Science Foundation under Grant No. DMR 78-01584.

DOI

https://doi.org/10.31274/rtd-180813-3525

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Eldon Darrel Case

Language

en

Proquest ID

AAI8103434

File Format

application/pdf

File Size

143 pages

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