Effect of Al Alloy Content on Processing of Reaction-Bonded Al2O3 Ceramics Using Al Alloy Powder

Abstract

The effect of Al content on the processing of reaction-bonded Al2O3 (RBAO) ceramics using 40v/o similar to 80v/o Al-Zn-Mg alloy powder was studied in order to improve traditional RBAO ceramic processes that use similar to 40v/o pure Al powder. The influence of high Al content in starting Al2O3-Al alloy powder mixtures on its particulate characteristics, reaction-bonding, microstructure, physical and mechanical properties was revealed. Starting Al2O3-Al alloy powder mixtures with 40v/o similar to 80v/o Al alloy powder were milled, reaction-bonded, post-sintered, and characterized. With an increasing Al alloy content, the milling efficiency of Al alloy powder was lowered, resulting in a larger particle size after milling. However, in spite of the larger particle size of Al alloy powder, the oxidation, i.e., reaction-bonding, of the Al alloy was successfully completed via solid and liquid state oxidation, in which the activation energy of the oxidation was nearly the same regardless of Al alloy content. After reaction-bonding and post-sintering at 1600 degrees C, RBAO ceramics from 80v/o Al alloy content showed a relative density of similar to 97% and a flexural strength of 251 MPa compared to similar to 96% and 353 MPa for RBAO ceramics from 40v/o Al alloy content, respectively. The lower flexural strength at 80v/o Al alloy content was due to the weak spinel phase that formed from Zn, Mg alloying elements in Al.