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Title: Metastability in the MgAl2O4-Al2O3 System

Aluminum oxide must take a spinel form ( γ-Al2O3) at elevated temperatures in order for extensive solid solution to form between MgAl2O4 and α-Al2O3. The solvus line between MgAl2O4 and Al2O3 has been defined at 79.6 wt% Al2O3 at 1500°C, 83.0 wt% Al2O3 at 1600°C, and 86.5 wt% Al2O3 at 1700°C. A metastable region has been defined at temperatures up to 1700°C which could have significant implications for material processing and properties. Additionally, initial processing could have major implications on final chemistry. The spinel solid solution region has been extended to form an infinite solid solution with Al2O3 at elevated temperatures. A minimum in melting at 1975°C and a chemistry of 96 wt% Al2O3 rather than a eutectic is present, resulting in no eutectic crystal formation during solidification.
Authors:
 [1] ;  [1] ;  [2]
  1. Missouri Univ. of Science and Technology, Rolla, MO (United States). Materials Science and Engineering
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Mechanical Properties & Mechanics Group
Publication Date:
OSTI Identifier:
1185327
Grant/Contract Number:
AC05-00OR22725; 14954
Type:
Accepted Manuscript
Journal Name:
International Journal of Applied Ceramic Technology
Additional Journal Information:
Journal Volume: 11; Journal Issue: 6; Journal ID: ISSN 1546-542X
Publisher:
Wiley
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE - Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY Spinel; Phase Diagram