Pressureless sintered magnesium aluminate spinel with enhanced mechanical properties obtained by the two-step sintering method

The effects of sintering parameters, first and second step sintering temperatures (T-1 and T-2, respectively), on the microstructure of magnesium aluminate spinel (MAS) were investigated. A single-step sintering (SSS) method was used to determine the appropriate temperatures for the first step. Different two-step sintering (TSS) regimes were used to investigate the effect of second step sintering temperatures on densification behavior and grain growth. The results show that, by using SSS method, the densification kinetics of MAS is different from grain growth kinetics. A MAS material with a high relative density of 96.17% and a homogeneous microstructure consisting of small grains (680 nm) is achieved under optimum TSS conditions (T-1 =1650 degrees C/0 h and T-2 = 1550 degrees C/10 h). Compared with conventional specimen, the bending strength (240 MPa) and Vickers hardness (11.05 GPa) of the sintered samples fabricated under optimum TSS increased by 54.8% and 52.2%, respectively. (C) 2016 Elsevier B.V. All rights reserved.