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NiAl has recently received much attention as a potential structural material because of its many superior high-temperature properties. The lack of high-temperature strength and fracture toughness and ductility at room temperature, however, limit the use of NiAl alloys. [1,2] Of the various attempts to enhance the ductility and high temperature strength, ductile refractory-metals, like Cr, Mo, W, Re and V, can successfully improve the mechanical properties of brittle NiAl by particle or dispersion strengthening and fiber reinforcement. [3][4][5][6] In particular, NiAl-28Cr-6Mo eutectic alloys are regarded as the most logical choice of the multicomponent system due to their relatively high melting point, low density, good thermal conductivity and high creep resistance [7][8][9] as well as higher fracture toughness compared to many NiAlbased alloys. Hafnium (Hf) was found to be very effective in improving the elevated temperature strength of NiAl-Cr(Mo) eutectic alloy. Unfortunately, Hf addition weakened the fracture toughness and ductility at room temperature severely. [10,11] For NiAl-Cr(Mo)/Hf lamellar eutectic alloy, the feasible way to improve the ductility and strength further is to reduce interlamellar spacing and microsegregation of solute element Hf. Solidification at high cooling rate is anticipated to attain such microstructure. Suction casting, as a popular method to fabricate bulk amorphous, [12,13] can obtain bulk NiAl alloys at a relatively high cooling rate of about 50 ∼ 10 2 K/s that is higher than 10 -1 ∼ 10 -2 K/s for the conventionally cast.Almost no work has been reported about the effect of suction casting technique on NiAl-Cr(Mo) eutectic alloys so far. Hence, the microstructural evolution and mechanical properties of NiAl-28Cr-5.5Mo-0.5Hf alloy prepared by conventionally cast and suction casting were investigated. The results show that suction casting technique markedly improves the COMMUNICATIONS 256

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