Cyclic thermal shock resistance for MgAlON-MgO composites obtained with additions of spent MgO-C brick: Microstructure characteristics, thermal shock parameter and thermal shock mechanism

Thermal shock parameters (R, R''', R'''' and R-st) of MgAlON-MgO composites obtained with additions of spent MgO-C brick were calculated using measured mechanical properties and thermal expansion coefficient, determining their resistance to fracture initiation and crack propagation. The cyclic thermal shock experiments of MgAlON-MgO composites performed from 1398 K to ambient temperature indicate that as number of thermal shock cycle increases, retained strength ratio of MgAlON and MgAlON-4.2 wt%MgO sharply decrease and then keep constant, while that of MgAlON-10.5 wt%MgO and MgAlON-15.7 wt%MgO slowly decrease. The reason for the difference is that MgAlON and MgAlON-4.2 wt%MgO show low value of R''' and R'''', and high value of R and R-st. Moreover, precipitation of impurity containing Fe may play a positive role in improvement of thermal shock resistance of MgAlON-MgO composites. MgAlON?4.2 wt%MgO has the maximum retained strength (55 MPa) even after 5 thermal shock cycles, which is expected to be used in the metallurgical industry.