采用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)、X射线衍射分析(XRD)和显微硬度计,研究了超重力场对A197.2Ni2.5Cro.3合金凝固组织及显微硬度的影响.结果表明,超重力场凝固试样的显微组织可以分为两部分,一是心部区域占80％以上,为Al-Al3Ni共晶组织;二是表层组织占20％以下,由初生a-Al和Al-Al3Ni共晶组织组成.超重力场可以细化合金组织,当超重力系数G为3 000时,初生a-Al细化最明显,平均晶粒尺寸为10.13 μm;当G为2 000时,Al3Ni细化最明显,棒状共晶直径和棒状共晶间距分别为72 nm和92 nm;超重力凝固试样中,合金的心部硬度高于表层硬度.心部区域和表层组织不同的主要原因是两者的Ni含量不同,而这是由于超重力场下对流加剧导致溶质原子易于扩散.“,”The effects of super-gravity field on the solidification structures and microhardness of Al97.2 Ni2.5Cr0.3 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-Al3Ni eutectic structure with more than 80 ％,and the second part is composted of a-Al primary grains and Al-Al3Ni 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 of a-Al reaches the minimum value of 10.13 μm under the gravity coefficient of G=3 000,and the diameter and spacing of Al3Ni 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.