The effects of super-gravity field on the solidification structures and microhardness of Al97.2 Ni2.5 Cr0.3 alloy were investigated by OM（optical microscopy）

SEM（scanning electron microscopy）

EDS（energy dispersed sperctrometer）

XRD（X-ray diffraction）and hardness testing.The results show that the solidification microstructure of sample under super-gravity field can be divided into two parts that the main part in the intermediate region is the Al-Al3 Ni eutectic structure with more than 80%

and the second part is composted ofα-Al primary grains and Al-Al3 Ni eutectic structure in the surface region with less than 20%.The grains in the alloy can be refined obviously under super-gravity field.With the increase of gravity coefficient

the average grain size is decreased firstly and then increased.The diameter ofα-Al reaches the minimum value of 10.13μm under the gravity coefficient of G=3 000

and the diameter and spacing of Al3 Ni reaches the minimum value of 72 and 92 nm

under the gravity coefficient of G=2 000

respectively.Under the super-gravity field

the hardness of alloy in the core is the greater than that of the surface

which is mainly attributed to fine-grain strengthening mechanism.Difference of the solidification microstructure at the core and surface of sample is the difference of Ni content

which is caused by diffusion of the solute atoms due to the increased convection under the supergravity conditions.