Investigation of compression deformation behavior and microstructure evolution of NiAl-Cr(Mo)-Hf alloy at eelevated temperature

NiAl-based alloy is a promising material applied in the fields of aeronautic and astronautic instruments. In the paper the compression deformation behavior and microstructure evolution of NiAl-Cr(Mo)-Hf` alloy at elevated temperature were studied. The results demonstrate that the alloy behaves good formability in the temperature ranging from 1320 degrees C similar to 1360 degrees C, in which the maximum initial strain rate is about 8.3 x 10(-4)s(-1) and the maximum deformation resistance is lower than 40MPa. During compression at temperature between 1250 degrees C and 1300 degrees C the flow stress increased sharply with the increasing of the deformation degree. When compression deformation at 1320 degrees C similar to 1360 degrees C, the flow stress decreased obviously and the flow stress decreased slightly after reached the maximum value. By analyzing the microstructure evolution during compression it can be concluded that as-casting microstructure was improved in deformation. The grains were refined and the brittle phases of lamellar Cr(Mo) existing at NiAl matrix were broken. The porosities in as-casting material were eliminated during compression and the density of the material increased. The fracture toughness of the alloy increased from 6AMPa center dot m(1/2) to 9.8MPa center dot m(1/2) after compression.