In order to develop a new type of contact cable with high strengthand high electrical conductivity, Cu-Cr alloy series were selected asmaterials and cu-Cr alloy castings were produced by means ofdirectional solidifica...In order to develop a new type of contact cable with high strengthand high electrical conductivity, Cu-Cr alloy series were selected asmaterials and cu-Cr alloy castings were produced by means ofdirectional solidification continu- ous casting (DSCC) process. theresults show that the fibrillar strengthening phase, β-Cr, orderlyarranges among the copper matrix phase along the wire direction; andmicrostructure of in-situ composite forms, which retains the basicproperty of good conductivity of the copper matrix and meanwhileobtains the strengthening effect ofβ-Cr phase.展开更多
The high-temperature tensile fracture behavior of the Ni, Cr, Al-TaC eutectic superal-loy directionally solidified under high temperature gradient is investigated. The high-temperature tensile fracture of this in situ...The high-temperature tensile fracture behavior of the Ni, Cr, Al-TaC eutectic superal-loy directionally solidified under high temperature gradient is investigated. The high-temperature tensile fracture of this in situ composite has ductile character with lots of ductile nests whose diameters decrease with the increasing solidification rates. The maximum σb and δ are respectively 668.5MPa and 19.6%. There is α TaC whisker in the center of each nest, and the deformation of γ' and TaC is uneven. The high-temperature tensile behavior cannot be explained by the rule of mixtures but is decided by the formation of the plastic deformation band. The crack extension model is given.展开更多
The directionally solidified samples of an ultra-high temperature Nb-Si-Ti-Hf-Cr-Al alloy have been prepared with the use of an electron beam floating zone melting (EBFZM) furnace, and their microstructural characteri...The directionally solidified samples of an ultra-high temperature Nb-Si-Ti-Hf-Cr-Al alloy have been prepared with the use of an electron beam floating zone melting (EBFZM) furnace, and their microstructural characteristics have been analyzed. All the primary dendrites of Nb solid solution (Nbss), eutectic colonies of Nba, plus (Nb, Ti)3 Si/(Nb, Ti)5 Si3 and chains of (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates align along the growth direction of the samples. With increasing of the withdrawing rate, the microstructure is refined, and the amounts of Nbss+ (Nb, Ti)3 Si/(Nb, Ti)5 Si3 eutectic colonies and (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates increase. There appear nodes in the (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates.展开更多
Directional solidification of rod-like eutectic is an important route to produce in situ composites.The rod-like phase spacing of composites is a crucial parameter in determining the properties of the materials.In thi...Directional solidification of rod-like eutectic is an important route to produce in situ composites.The rod-like phase spacing of composites is a crucial parameter in determining the properties of the materials.In this study,the rod-like phase spacing of melt-grown in situ eutectic composites is estimated by the method that is established based on the classical Jackson-Hunt theory and completed by considering the minimum undercooling principle in eutectic solidification at steady state.The density difference between the solid phases is also considered when calculating the diffusion field in the liquid.It is found that the rod-like phase spacing of in situ eutectic composites is generally a not unique value but displays a finite range under fixed growth conditions.Also,the range width,which decreases with increasing growth rate and vice versa,is only dependent on the intrinsic properties of an alloy at a given growth rate.By comparing with the experimental observations,the results show that the predicted spacings are in reasonable agreement with experimental data for nonfaceted-nonfaceted Succinonitrile-(D)camphor,MnSb-Sb,and Al-Al3Ni alloys and faceted-nonfaceted MnBi-Bi system when growing in a coupled manner.展开更多
文摘In order to develop a new type of contact cable with high strengthand high electrical conductivity, Cu-Cr alloy series were selected asmaterials and cu-Cr alloy castings were produced by means ofdirectional solidification continu- ous casting (DSCC) process. theresults show that the fibrillar strengthening phase, β-Cr, orderlyarranges among the copper matrix phase along the wire direction; andmicrostructure of in-situ composite forms, which retains the basicproperty of good conductivity of the copper matrix and meanwhileobtains the strengthening effect ofβ-Cr phase.
基金supported by the National Natural Science Foundation of China(No.50102004)the Aeronautical Science Foundation of China(No.97G53066)the Developing Program for Outstanding Persons in NPU,China.
文摘The high-temperature tensile fracture behavior of the Ni, Cr, Al-TaC eutectic superal-loy directionally solidified under high temperature gradient is investigated. The high-temperature tensile fracture of this in situ composite has ductile character with lots of ductile nests whose diameters decrease with the increasing solidification rates. The maximum σb and δ are respectively 668.5MPa and 19.6%. There is α TaC whisker in the center of each nest, and the deformation of γ' and TaC is uneven. The high-temperature tensile behavior cannot be explained by the rule of mixtures but is decided by the formation of the plastic deformation band. The crack extension model is given.
基金supported by the National Natural Science Foundation of China(No.50271056)National High Technical Research and Development Programme of China(No.2003AA305810)the Special Research Fund for Doctoral Disciplines in Colleges and Universities of M.0.E,China(No.20020699025).
文摘The directionally solidified samples of an ultra-high temperature Nb-Si-Ti-Hf-Cr-Al alloy have been prepared with the use of an electron beam floating zone melting (EBFZM) furnace, and their microstructural characteristics have been analyzed. All the primary dendrites of Nb solid solution (Nbss), eutectic colonies of Nba, plus (Nb, Ti)3 Si/(Nb, Ti)5 Si3 and chains of (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates align along the growth direction of the samples. With increasing of the withdrawing rate, the microstructure is refined, and the amounts of Nbss+ (Nb, Ti)3 Si/(Nb, Ti)5 Si3 eutectic colonies and (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates increase. There appear nodes in the (Nb, Ti)3 Si/(Nb, Ti)5 Si3 plates.
基金supported by the National Natural Science Foundation of China(Grant Nos.50971102,50201012)the Natural Science Foundation of the Shaanxi Education Committee,China(Grant No.14JK1363)
文摘Directional solidification of rod-like eutectic is an important route to produce in situ composites.The rod-like phase spacing of composites is a crucial parameter in determining the properties of the materials.In this study,the rod-like phase spacing of melt-grown in situ eutectic composites is estimated by the method that is established based on the classical Jackson-Hunt theory and completed by considering the minimum undercooling principle in eutectic solidification at steady state.The density difference between the solid phases is also considered when calculating the diffusion field in the liquid.It is found that the rod-like phase spacing of in situ eutectic composites is generally a not unique value but displays a finite range under fixed growth conditions.Also,the range width,which decreases with increasing growth rate and vice versa,is only dependent on the intrinsic properties of an alloy at a given growth rate.By comparing with the experimental observations,the results show that the predicted spacings are in reasonable agreement with experimental data for nonfaceted-nonfaceted Succinonitrile-(D)camphor,MnSb-Sb,and Al-Al3Ni alloys and faceted-nonfaceted MnBi-Bi system when growing in a coupled manner.
