Abstract
The influence of high-temperature aging heat treatment on microstructure and hardness of single crystal Ni3Al-base superalloy IC21 were investigated. The results showed that the temperature and time of aging treatment had significant effect on the shape and the average size of γ’ precipitate as well as the hardness of the alloy. The average size and volume fraction of γ’ precipitate after 1320°C/10h/Ar cooling+870°C/32h/air cooling(AC) treatment were about 270nm and 63% respectively. The experimental results showed that the two-step aging treatment following the solution treatment significantly influenced the size and volume fraction of γ’ phase, i.e., through the treatment of 1320°C/10h/Ar cooling +1060°C/2h/AC+870°C/32h/AC the moderate size (about 450nm) and volume fraction (about 70%) of cubic γ’ phase obtained and the hardness of the alloy reached the maximum value of about 370HV. However, with the increase of the aging temperature or time the size and the volume fraction of γ’ precipitate increased and the morphology of the γ’ precipitate gradually changed from cubic shape to rod shape. It has been found that after 1320°C/10h/Ar cooling +1120°C/2h/AC+870°C/32h/AC or 1320°C/10h/Ar cooling +1060°C/6h/AC+870°C/32h/AC treatment the morphology of the γ’ precipitates obviously changed from cubic shape to rod shape and the hardness of the alloy decreased significantly.
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