Al

2

O

3

/ZrO

2

（4Y） self-growing composite ceramics

which is composed of major rod-shaped sapphires with 8.0

1

2.0 aspect ratio and minor lamellar α-Al

2

O

3

phase

and within the sapphires t-ZrO

2

nano-micron fibers are embedded

has been prepared with eutectic growth of melts in the condition of severe undercooling degree by introducing proper ZrO

2

（4Y） powder into the thermit on the basis of oxidation-reduction reaction of the thermit and liquid-liquid phase separation of ceramics/metal under the gravity

the relationship of microstructure with mechanical behavior has been understood by measuring mechanical properties of the composites and observing crack propagation paths. The results show that the flexural strength and fracture toughness of ceramic composites are 1 256 MPa and 13.2 MPa·m

1/2

respectively. A number of low energy interface in a nano-micron scale distance between Al

2

O

3

/ZrO

2

（4Y） and compressive residual stress in the sapphires results in the reinforcement of the rod-shaped sapphires and ceramics matrix

which exerts the crack to propagate along the rod-shaped sapphires. Meanwhile

crack-bridging and pull-out of sapphires

crack-bridging and frictionally interlocked effects of plate-like α- Al

2

O

3

grain in the wake of crack tip also render the crack stabilization to arise.