The influence of melt convection on dendrite growth during the upward-directional solidification of Pb-33%Sn binary alloys was investigated.The melt convection was modulated by traveling magnetic field.When the direct...The influence of melt convection on dendrite growth during the upward-directional solidification of Pb-33%Sn binary alloys was investigated.The melt convection was modulated by traveling magnetic field.When the direction of traveling magnetic field was changed from upward to downward,the primary dendrite spacing gradually increased,and the distribution peak of the primary dendrite spacing shifted to the field of narrower spacing.These result from the different intensities of melt convection,which are controlled by the traveling magnetic field.The effects of the traveling magnetic field on melt convection are similar to those of adjustment in the gravity level,thus,the primary dendrite spacing varies.When the intensity of the traveling magnetic field was 1 mT,and the drawing speed was 50 μm/s,the gravity acceleration reached 0.22g for the downward-traveling magnetic field and 3.07g for the upward-traveling magnetic field.展开更多
Directional solidification experiments were conducted for Ti-46Al-8Nb alloy at the growth rates ranging from 3 to 70 pards. The microstructure evolution and microsegregation pattern were investigated. In the range of ...Directional solidification experiments were conducted for Ti-46Al-8Nb alloy at the growth rates ranging from 3 to 70 pards. The microstructure evolution and microsegregation pattern were investigated. In the range of growth rate, a regular dendritic structure appears and the primary dendrite spacing decreases with increasing growth rate. The peritectic reaction is observed during the solidification and the final microstructure is composed of α2/γ lamellar structure and retained β（B2） after directional solidification The lamellar orientation is found to be parallel and 45° to the primary growth direction ofβ dendrite. Peritectic reaction leads to significant chemical inhomogeneity, in which aluminum is rich in interdendritic liquid and niobium is rich in the core ofβ dendrite during the solidification. With the nucleation and growth of a phase, the segregation amplitude of niobium increases, which promotes the formation of B2 phase, while aluminum rich in the interdendritic becomes homogeneous gradually.展开更多
Peritectic reaction was studied by directional solidification of Cu-Ge alloys.A larger triple junction region of peritectic reaction was used to analyze the interface stability of the triple junction region during per...Peritectic reaction was studied by directional solidification of Cu-Ge alloys.A larger triple junction region of peritectic reaction was used to analyze the interface stability of the triple junction region during peritectic reaction.Under different growth conditions and compositions,different growth morphologies of triple junction region are presented.For the hypoperitectic Cu-13.5%Ge alloy,as the pulling velocity（v） increases from 2 to 5 μm/s,the morphological instability of the peritectic phase occurs during the peritectic reaction and the remelting interface of the primary phase is relatively stable.However,for the hyperperitectic Cu-15.6%Ge alloy wim v=5 μm/s,the nonplanar remelting interface near the trijunction is presented.The morphological stabilities of the solidifying peritectic phase and the remelting primary phase are analyzed in terms of the constitutional undercooling criterion.展开更多
In the production of AlCuFe alloy for a special application,the growth rate was changed and the results were evaluated.Changes in the eutectic spacing(microstructure)of a material due to the growth rate are known to a...In the production of AlCuFe alloy for a special application,the growth rate was changed and the results were evaluated.Changes in the eutectic spacing(microstructure)of a material due to the growth rate are known to affect its mechanical,electrical and thermal properties.To evaluate its microstructure,the eutectic composition of Al−32.5wt.%Cu−0.5wt.%Fe was prepared and directional solidification experiments were conducted using a Bridgman-type furnace at a constant temperature gradient(G=8.50 K/mm)and five growth rates(V=8.25,16.60,41.65,90.05,164.80μm/s).The effect of the growth rate on the eutectic spacing was then determined,and the resulting microhardness and ultimate tensile strength were obtained based on the change in the microstructure by regression analysis and Hall−Petch correlations.Despite the fact that the growth rate increased by approximately twenty times,the eutectic spacing decreased by a factor of approximately 5,and these changes in the growth rate and microstructure caused the mechanical properties to change by a factor of approximately 1.5.展开更多
Sn-36%Ni peritectie alloys were directionally solidified at different growth rates under a constant temperature gradient （20 K/mm）, the dependences of microstructural characteristic length scales on the growth rate ...Sn-36%Ni peritectie alloys were directionally solidified at different growth rates under a constant temperature gradient （20 K/mm）, the dependences of microstructural characteristic length scales on the growth rate were investigated. Experimental results are presented, including primary and higher order dendrite arm spacings 21, 22, 23 and dendrite tip radius R of primary NisSn2 phase. Comparisons between the theoretical predictions and the experimental results show that, for the primary dendrites, 21=335.882v-0.21, which is in agreement with the Kurz-Fisher model; for the secondary dendrites, λ2=44.957v-0.277, which is consistent with the Bouchard-Kirkaldy model; for the tertiary dendrites, λ3=40.512v-0.274; for the dendrite tip radius, R=22.7v-0.36. The experimental results also show that the 21/22 changes greatly with increasing growth rate while the 21/23 has no significant change, indicating that tertiary dendrite arms have a more similar growth characteristics to primary dendrites compared with secondary dendrites. The λ1/R ranges from 2 to 2.3 with the increase of growth rate. Key words： Sn-Ni alloy; directional solidification; dendrite arm spacing; dendrite tip radius展开更多
Zn-5%Al-0.2%Bi（mass fraction） alloy was directionally solidified upward at a constant temperature gradient with a wide range of growth rates using a Bridgman-type directional solidification furnace. The eutectic spa...Zn-5%Al-0.2%Bi（mass fraction） alloy was directionally solidified upward at a constant temperature gradient with a wide range of growth rates using a Bridgman-type directional solidification furnace. The eutectic spacings, microhardness, ultimate tensile strength and electrical resistivity for directionally solidified Zn-Al-Bi alloy were measured. Dependence of eutectic spacings, microhardness, ultimate tensile strength and electrical resistivity on growth rates was obtained by linear regression analysis. The results obtained in the present work for low growth rates（smaller than 450.0 μm/s） are in good agreement with experimental results obtained in previous work for directional solidified Zn-Al eutectic alloy with a similar growth rate but differs from the Jackson-Hunt eutectic theory and those obtained in previous experimental works at higher growth rates. The critical growth rate might be 450.0 μm/s for the Zn-Al-Bi eutectic alloy. From the plot of heat flow versus temperature, enthalpy of fusion, specific heat difference between liquid and solid phases and melting temperature for the Zn-Al-Bi alloy are found to be 112.55 J/g, 0.291 J/（g·K） and 660.20 K, respectively.展开更多
基金Project(50827102)supported by the National Natural Science Foundation of ChinaProject(2010CB631202)supported by the National Basic Research Program of ChinaProject(28-TP-2009)supported by Research Fund of State Key Laboratory of Solidification Processing(NWPU),China
文摘The influence of melt convection on dendrite growth during the upward-directional solidification of Pb-33%Sn binary alloys was investigated.The melt convection was modulated by traveling magnetic field.When the direction of traveling magnetic field was changed from upward to downward,the primary dendrite spacing gradually increased,and the distribution peak of the primary dendrite spacing shifted to the field of narrower spacing.These result from the different intensities of melt convection,which are controlled by the traveling magnetic field.The effects of the traveling magnetic field on melt convection are similar to those of adjustment in the gravity level,thus,the primary dendrite spacing varies.When the intensity of the traveling magnetic field was 1 mT,and the drawing speed was 50 μm/s,the gravity acceleration reached 0.22g for the downward-traveling magnetic field and 3.07g for the upward-traveling magnetic field.
基金Projects (50801019,51071062) supported by the National Natural Science Foundation of ChinaProject (2011CB605504) supported by the National Basic Research Program of China
文摘Directional solidification experiments were conducted for Ti-46Al-8Nb alloy at the growth rates ranging from 3 to 70 pards. The microstructure evolution and microsegregation pattern were investigated. In the range of growth rate, a regular dendritic structure appears and the primary dendrite spacing decreases with increasing growth rate. The peritectic reaction is observed during the solidification and the final microstructure is composed of α2/γ lamellar structure and retained β（B2） after directional solidification The lamellar orientation is found to be parallel and 45° to the primary growth direction ofβ dendrite. Peritectic reaction leads to significant chemical inhomogeneity, in which aluminum is rich in interdendritic liquid and niobium is rich in the core ofβ dendrite during the solidification. With the nucleation and growth of a phase, the segregation amplitude of niobium increases, which promotes the formation of B2 phase, while aluminum rich in the interdendritic becomes homogeneous gradually.
基金Projects (50901025,50975060,51331005) supported by the National Natural Science Foundation of ChinaProject (2011CB610406) supported by the National Basic Research Program of China+2 种基金Projects (201104420,20090450840) supported by China Postdoctoral Science FoundationProject (JC201209) supported by Outstanding Young Scientist Foundation of Heilongjiang Province,ChinaProject (HIT.BRET1.20100008) supported by the Fundamental Research Funds for Central Universities,China
文摘Peritectic reaction was studied by directional solidification of Cu-Ge alloys.A larger triple junction region of peritectic reaction was used to analyze the interface stability of the triple junction region during peritectic reaction.Under different growth conditions and compositions,different growth morphologies of triple junction region are presented.For the hypoperitectic Cu-13.5%Ge alloy,as the pulling velocity（v） increases from 2 to 5 μm/s,the morphological instability of the peritectic phase occurs during the peritectic reaction and the remelting interface of the primary phase is relatively stable.However,for the hyperperitectic Cu-15.6%Ge alloy wim v=5 μm/s,the nonplanar remelting interface near the trijunction is presented.The morphological stabilities of the solidifying peritectic phase and the remelting primary phase are analyzed in terms of the constitutional undercooling criterion.
基金This research was supported financially by the Scientific and Technical Research Council of Turkey(TUBİTAK)under Contract No.112T588The author is grateful to the Scientific and Technical Research Council of Turkey(TUBİTAK)for its financial support。
文摘In the production of AlCuFe alloy for a special application,the growth rate was changed and the results were evaluated.Changes in the eutectic spacing(microstructure)of a material due to the growth rate are known to affect its mechanical,electrical and thermal properties.To evaluate its microstructure,the eutectic composition of Al−32.5wt.%Cu−0.5wt.%Fe was prepared and directional solidification experiments were conducted using a Bridgman-type furnace at a constant temperature gradient(G=8.50 K/mm)and five growth rates(V=8.25,16.60,41.65,90.05,164.80μm/s).The effect of the growth rate on the eutectic spacing was then determined,and the resulting microhardness and ultimate tensile strength were obtained based on the change in the microstructure by regression analysis and Hall−Petch correlations.Despite the fact that the growth rate increased by approximately twenty times,the eutectic spacing decreased by a factor of approximately 5,and these changes in the growth rate and microstructure caused the mechanical properties to change by a factor of approximately 1.5.
基金Projects （51071062, 51271068, 51274077） supported by the National Natural Science Foundation of China Project （2011 -P03） supported by Open Fund of State Key Laboratory of Mold and Die Technology of Huazhong University of Science and Technology, China+1 种基金 Project （HIT. NSRIF. 2013002） supported by the Fundamental Research Funds for the Central Universities, China Project （2011CB610406） supported by the National Basic Research Program of China
文摘Sn-36%Ni peritectie alloys were directionally solidified at different growth rates under a constant temperature gradient （20 K/mm）, the dependences of microstructural characteristic length scales on the growth rate were investigated. Experimental results are presented, including primary and higher order dendrite arm spacings 21, 22, 23 and dendrite tip radius R of primary NisSn2 phase. Comparisons between the theoretical predictions and the experimental results show that, for the primary dendrites, 21=335.882v-0.21, which is in agreement with the Kurz-Fisher model; for the secondary dendrites, λ2=44.957v-0.277, which is consistent with the Bouchard-Kirkaldy model; for the tertiary dendrites, λ3=40.512v-0.274; for the dendrite tip radius, R=22.7v-0.36. The experimental results also show that the 21/22 changes greatly with increasing growth rate while the 21/23 has no significant change, indicating that tertiary dendrite arms have a more similar growth characteristics to primary dendrites compared with secondary dendrites. The λ1/R ranges from 2 to 2.3 with the increase of growth rate. Key words： Sn-Ni alloy; directional solidification; dendrite arm spacing; dendrite tip radius
基金supported by Erciyes University Scientific Research Project Unit under Contract No:FYL-2013-4841
文摘Zn-5%Al-0.2%Bi（mass fraction） alloy was directionally solidified upward at a constant temperature gradient with a wide range of growth rates using a Bridgman-type directional solidification furnace. The eutectic spacings, microhardness, ultimate tensile strength and electrical resistivity for directionally solidified Zn-Al-Bi alloy were measured. Dependence of eutectic spacings, microhardness, ultimate tensile strength and electrical resistivity on growth rates was obtained by linear regression analysis. The results obtained in the present work for low growth rates（smaller than 450.0 μm/s） are in good agreement with experimental results obtained in previous work for directional solidified Zn-Al eutectic alloy with a similar growth rate but differs from the Jackson-Hunt eutectic theory and those obtained in previous experimental works at higher growth rates. The critical growth rate might be 450.0 μm/s for the Zn-Al-Bi eutectic alloy. From the plot of heat flow versus temperature, enthalpy of fusion, specific heat difference between liquid and solid phases and melting temperature for the Zn-Al-Bi alloy are found to be 112.55 J/g, 0.291 J/（g·K） and 660.20 K, respectively.
