Abstract:

The microstructural characterizations of Ni (4～6)Al 20Hf 8Cr 8W system alloys have been examined by optical micrograph,TEM,SEM,Electron Microprobe and X ray diffraction. In particular, the influence of aluminium content was studied in detail. A slight difference of the aluminum content can change obviously the microstructure and bring about eutectic phases. The γ′+Ni 7Hf 2,γ+γ′+Ni 7Hf 2 or γ+Ni 7Hf 2 eutectic was present in low Al content alloys(<5.5wt%) ,and the β+Ni 7Hf 2 or γ+β NiAl+Ni 7Hf 2 eutectic in high content alloys(>5.5 wt%) . Ni 5.3Al 20Hf 8Cr 8W is the proper composition as the γ′/Ni 7Hf 2 eutectic composite materials.

Key words: Ni Al Hf Cr W alloys, in situ composite material, Ni 7Hf 2phase, eutectic, microstructure