This paper explains the principle of a newly developed ZMLMC directional solidification apparatus with a superhigh temperature gradient.With the help of the apparatus,research was done on the change of directional sol...This paper explains the principle of a newly developed ZMLMC directional solidification apparatus with a superhigh temperature gradient.With the help of the apparatus,research was done on the change of directional solidification structures of the cobalt based superalloy K10 at superhigh velocities.Relations between the primary and secondary dendrite arm spacings and the cooling rates Were investigated.Experimental results show that the primary and secondary dendrite arm spacings of directionally solidified cobalt based superalloys are respectively finer than one fifth and one eighth of those produced by conventional directional soli-dification processes.The primary and secondary dendrite arm spacing which can be decreased by increasing the cooling rate,and the relations between these spacings(λ1,λ2)and the temperature gradient(G)and solidfication rate(v)were as follows:λ1=1.428×10^(3)(G·v)^-1_(1)λ_(2)=0.132×10^(3)(G·v)^-1.展开更多
Lotus-type porous silicon with elongated pores was fabricated by unidirectional solidification under pressurized hydrogen. Porosity, pore diameter, and pore length can be adjusted by changing solidification speed and ...Lotus-type porous silicon with elongated pores was fabricated by unidirectional solidification under pressurized hydrogen. Porosity, pore diameter, and pore length can be adjusted by changing solidification speed and hydrogen pressure. The porosity of the ingot is nearly constant under different solidification speeds, but decreases with the increase of hydrogen pressure. The overall porosities of ingots fabricated at different hydrogen pressures were evaluated through a theoretical model. Findings are in good agreement with experimental values. The average pore diameter and pore length increase simultaneously while the average pore aspect ratio changes slightly with the decreases of solidification speed and hydrogen pressure. The average pore length is raised from 7 to 24 mm and the pore aspect ratio is raised from 8 to 20 respectively with the average pore diameter promoted by about 0.3 mm through improving the superheat degree of the melt from 200 to 300 K.展开更多
基金supported by China National Natural Science foundation。
文摘This paper explains the principle of a newly developed ZMLMC directional solidification apparatus with a superhigh temperature gradient.With the help of the apparatus,research was done on the change of directional solidification structures of the cobalt based superalloy K10 at superhigh velocities.Relations between the primary and secondary dendrite arm spacings and the cooling rates Were investigated.Experimental results show that the primary and secondary dendrite arm spacings of directionally solidified cobalt based superalloys are respectively finer than one fifth and one eighth of those produced by conventional directional soli-dification processes.The primary and secondary dendrite arm spacing which can be decreased by increasing the cooling rate,and the relations between these spacings(λ1,λ2)and the temperature gradient(G)and solidfication rate(v)were as follows:λ1=1.428×10^(3)(G·v)^-1_(1)λ_(2)=0.132×10^(3)(G·v)^-1.
基金Project(51271096)supported by the National Natural Science Foundation of ChinaProject(NCET-12-0310)supported by the Program for New Century Excellent Talents in University,China
文摘Lotus-type porous silicon with elongated pores was fabricated by unidirectional solidification under pressurized hydrogen. Porosity, pore diameter, and pore length can be adjusted by changing solidification speed and hydrogen pressure. The porosity of the ingot is nearly constant under different solidification speeds, but decreases with the increase of hydrogen pressure. The overall porosities of ingots fabricated at different hydrogen pressures were evaluated through a theoretical model. Findings are in good agreement with experimental values. The average pore diameter and pore length increase simultaneously while the average pore aspect ratio changes slightly with the decreases of solidification speed and hydrogen pressure. The average pore length is raised from 7 to 24 mm and the pore aspect ratio is raised from 8 to 20 respectively with the average pore diameter promoted by about 0.3 mm through improving the superheat degree of the melt from 200 to 300 K.
