Microstructure characteristics and mechanical properties of Al2O3/MgAl2O4 directionally solidified eutectic ceramic

ABSTRACT Al2O3/MgAl2O4 directionally solidified eutectic ceramic (DSEC) rods with Φ 10 mm were prepared with induction heating zone melting (IHZM) method. The phase components of the DSEC were composed of MgAl2O4 phase growing along the preferred orientation 〈311〉 and Al2O3 phases growing along the preferred orientation 〈110〉. In the DSEC, the Al2O3 phase is the matrix phase mixed with part of MgAl2O4 phase and the other part of MgAl2O4 phase forms slice structure. Both the DSEC density and hardness decrease with the increase of the growth rate, due to the increase of micropores in DSEC with the higher growth rate. However, its fracture toughness improved due to the fine interface spacing toughening and the dispersion toughening. The highest hardness and fracture toughness of DSEC are 19.3 GPa and 3.74 MPa·m1/2, respectively, the toughening effect could be attributed to the crack deflection and bifurcation hindering the propagation of crack in DSEC.