The effect of solidification rate on the microstructure development of nickel-based superalloy under the temperature gradient of 500 K·cm-1 was studied. The results show that, with the increase of directional sol...The effect of solidification rate on the microstructure development of nickel-based superalloy under the temperature gradient of 500 K·cm-1 was studied. The results show that, with the increase of directional solidification rate from 50 to 800 μm·s-1, both the primary and the secondary dendrite arm spacings of the alloy decrease gradually, and the dendrite morphologies transform from coarse dendrite to superfine dendrite. The sizes of all precipitates in the superalloy decrease gradually. The morphology of γ' precipitate changes from cube to sphere shape and distributes uniformly in both dendrite core and interdendritic regions. MC carbide morphology changes from coarse block to fine-strip and then to Chinese-script and mainly consists of Ta, W, and Hf elements. The γ-γ' eutectic fraction increases firstly and then decreases, and similar regularity is also found for the variation of segregation ratio of elements.展开更多
Microbial transformation of diosgenin(1) was carried out with the white-rot fungus,Coriolus versicolor.A new polyhydroxyl metabolite,(25R)-spirost-5-ene-3β,7β,21-triol(2),was obtained as a result of hydroxylation.It...Microbial transformation of diosgenin(1) was carried out with the white-rot fungus,Coriolus versicolor.A new polyhydroxyl metabolite,(25R)-spirost-5-ene-3β,7β,21-triol(2),was obtained as a result of hydroxylation.Its structure was elucidated on the basis of 1D and 2D NMR as well as HR-ESI-MS spectroscopic analysis.展开更多
基金financially supported by National Natural Science Foundation of China(No.50827102)the Scientific Research Foundation for Ph.D.,Northwest A&F University(No.Z109021103)+1 种基金the Special Fund for Basic Scientific Research of Central Colleges,Northwest A&F University(No.Z109021114)the Fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201220)
文摘The effect of solidification rate on the microstructure development of nickel-based superalloy under the temperature gradient of 500 K·cm-1 was studied. The results show that, with the increase of directional solidification rate from 50 to 800 μm·s-1, both the primary and the secondary dendrite arm spacings of the alloy decrease gradually, and the dendrite morphologies transform from coarse dendrite to superfine dendrite. The sizes of all precipitates in the superalloy decrease gradually. The morphology of γ' precipitate changes from cube to sphere shape and distributes uniformly in both dendrite core and interdendritic regions. MC carbide morphology changes from coarse block to fine-strip and then to Chinese-script and mainly consists of Ta, W, and Hf elements. The γ-γ' eutectic fraction increases firstly and then decreases, and similar regularity is also found for the variation of segregation ratio of elements.
基金supported by the National Natural Science Foundation of China(No.30770237)the Program for New Century Excellent Talents in University(No.NCET-05-0852)
文摘Microbial transformation of diosgenin(1) was carried out with the white-rot fungus,Coriolus versicolor.A new polyhydroxyl metabolite,(25R)-spirost-5-ene-3β,7β,21-triol(2),was obtained as a result of hydroxylation.Its structure was elucidated on the basis of 1D and 2D NMR as well as HR-ESI-MS spectroscopic analysis.
