By introducing ZrO2（4Y）powder into the thermit

the large-scale plates of new Al

2

O

3

/ZrO2（4Y）composite ceramics with various component and structure were prepared by combustion synthesis under high gravity

and the correlation of component

microstructure and mechanical properties of composite ceramics were investigated by XRD（X-ray diffraction）

SEM（scanning electron microscope）and EDS（energy dispersive spectrum）.The results reveal that Al

2

O

3

/33ZrO2（4Y）is composed of random-oriented rode-shape colonies embedding by a triangular dispersion of orderly t-ZrO2 submicron fibers

surrounded by inter-colony regions consisting of nano-micrometer spherically-shape t-ZrO2 grains

meanwhile

Al

2

O

3

/40ZrO2（4Y）is composed of micronmeter spherically-shape t-ZrO2

surrounded by irregular-shape α-Al

2

O

3

grains and a few colonies.Compared with the international directionally-solidified Al

2

O

3

/ZrO2（Y2O3）

the increase of hardness and flexural strength of Al

2

O

3

/33ZrO2（4Y）are attributed to high densification

small-size defects and high fracture toughness induced by compressive residual stress toughening and transformation toughening mechanism.In addition

in despite of the moderate decrease in hardness

flexural strength and fracture toughness are increased by 19.0% and 311.1%

respectively

which is attributed to the result of small-size defect in micron-meter spherically-shaped t-ZrO2 grain matrix and high fracture toughness induced by stress-induced t-ZrO2 transformation toughening and transformation-induced micro-crack toughening mechanisms.