Elevated temperature strength and room-temperature toughness of directionally solidified Ni-33Al-33Cr-1Mo

The eutectic composition Ni-33Al-33Cr-1Mo has been directionally solidified (DS) via a modified Bridgman technique at rates ranging from 7.6 to 508 mm/h to determine if the growth rate affects the mechanical properties. Microstructural examination revealed that all DS rods had grain/cellular microstructures containing alternating plates of NiAl and Cr alloyed with Mo. At slower growth rates (less than or equal to 12.7 mm/h), the grains had sharp boundaries, while faster growth rates (greater than or equal to 25.4 mm/h) led to cells bounded by intercellular regions. None of the growth conditions resulted in either dendrites or third phases. Compressive testing between 1200 and 1400 K indicated that alloys DS at rates between 25.4 and 254 mm/h possessed the best strengths, while room-temperature toughness exhibited a plateau of about 16 MParootm for growth rates between 12.7 and 127 mm/h. Thus, a growth rate of 127 mm/h represents the best combination of fast processing and mechanical properties for this system.