Abstract
Materials with gradient microstructures have a wide range of applications such as cutting tools, armor, and electronic devices. However, it is difficult to predict and control the gradient microstructure during processing. In the present work, a continuous porosity gradient was successfully achieved in ZnO material via spark plasma sintering with a large induced thermal gradient. The porosity is overestimated if isothermal prediction is applied. The current work proposed a more accurate prediction of the porosity by considering the stress-shielding effect caused by the thermal gradient. The shielding effect results from different stress states in the sample due to differential sintering: the hotter side of the specimen experiences a higher strain rate and more shrinkage while the colder side experiences a lower strain rate and less shrinkage simultaneously. Therefore, the axial strains are varied throughout the sample thickness. Using the constituent equations in advanced sintering analysis, the shield stress was calculated to be approximately 13 MPa for the viscoelastic assumption of sintering. To improve the accuracy of predicting porosity gradient, it is necessary to add a load to overcome the shield stress when the materials are sintered with a thermal gradient.
Original language | English |
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Pages (from-to) | 587-594 |
Number of pages | 8 |
Journal | Journal of the American Ceramic Society |
Volume | 102 |
Issue number | 2 |
DOIs | |
State | Published - 2018 |
Funding
This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).
Keywords
- Porosity gradient
- Prediction of microstructure
- Spark plasma sintering