Jian Zhang Jinguo Li Tao Jin Xiaofeng Sun Zhuangqi Hu
材料科学技术（英文）
A single crystal Ni-base superalloy was processed with withdrawal rates between 2 and 7 mm/min. The as-cast microstructures, heat treatment response and creep property have been characterized as a function of the withdrawal rate. As expected, the primary and secondary dendrite arm spacing decreased with increasing withdrawal rate; microsegregation degree and porosity distribution were also varied with different withdrawalrates. The withdrawal rate of 2 mm/min resulted in a noticeable residual microsegregation even after full heat treatment. The samples solidified at 7 mm/min exhibited a high density of cast porosities, and this led to a dramatical decline of the creep strain. 4 or 6 mm/min appeared to be the optimum withdrawal rate in the present study, which resulted in a uniform microstructure and an optimum density of cast porosity.
关键词:
Single crystal superalloy
,
Withdrawal rate
,
Microstructure
,
Creep
Chengbao Liu Jian Shen Jian Zhang Langhong Lou
材料科学技术（英文）
A nickel base single crystal (SC) superalloy was directionally solidified using liquid metal cooling (LMC) process at various withdrawal rates. The microstructure was refined as increasing the withdrawal rate from 3 to 12 mm/min. However, higher withdrawal rate of 15 mm/min induced the formation of stray grains. Size and volume fraction of the eutectics were found to decrease with the increasing in withdrawal rate. After solution heat treatment at 1250°C, un-dissolved eutectic was observed in specimens. High temperature creep rupture life was observed to be very sensitive to the fraction of these remaining eutectics. Creep rupture tests at 1000°C/235 MPa showed that refined microstructure and low fraction of the remaining eutectic lead to significant improvement of the rupture life.
关键词:
Eutectic
,
single crystal superalloy
,
liquid-metal-cooling
,
withdrawal rate
