Microstructure characteristics and mechanical properties of Al 2 O 3 /MgAl 2 O 4 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·m^1/2, respectively, the toughening effect could be attributed to the crack deflection and bifurcation hindering the propagation of crack in DSEC.