Experimental studies on the melting process of titanium aluminum alloy have been pursued from the viewpoint of contamination.TiAl alloys were prepared with vacuum induction melting （VIM） in calcia crucibles at 1873 ...Experimental studies on the melting process of titanium aluminum alloy have been pursued from the viewpoint of contamination.TiAl alloys were prepared with vacuum induction melting （VIM） in calcia crucibles at 1873 K and 1923 K in order to determine the behavior of the oxygen content as a function of temperature,time and frequency of power.The experiment results showed that alloys were uncontaminated except for the increasing of oxygen content which was introduced from the reaction CaO（s）=Ca（in TiAl）＋O（in TiAl）,and the standard Gibbs energy of the reaction was determined to be △G0 =274000 102.8T（J/mol）.Oxygen content increased slowly with the melting time by about 50×10-6 wt pct/min,and decreased with induction melting frequency.Lower superheat and higher melting frequency can be used to reduce oxygen content increasing rate.展开更多
The influence of crucible and vacuum on oxygen content of CuCr25 prepared by vacuum induction melting (VIM) has been investigated. The experimental results show that the selection of crucible is very important. Alkali...The influence of crucible and vacuum on oxygen content of CuCr25 prepared by vacuum induction melting (VIM) has been investigated. The experimental results show that the selection of crucible is very important. Alkaline oxide MgO crucible can result in increment of oxygen content and segregation of Cr in the CuCr25 alloys prepared. Neutral oxide Al 2O 3 crucible has no contribution to oxygen in CuCr25. The results also indicate that some kinds of deoxidant, such as Al, are further beneficial to deoxidization of the alloys. [展开更多
This study documents laboratory-scale observation of the interactions between the Ni-based superalloy FGH4096 and refractories.Three different crucibles were tested—MgO,Al2O3,and MgO–spinel.We studied the variations...This study documents laboratory-scale observation of the interactions between the Ni-based superalloy FGH4096 and refractories.Three different crucibles were tested—MgO,Al2O3,and MgO–spinel.We studied the variations in the compositions of the inclusions and the alloy–crucible interface with the reaction time using scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and Xray diffraction.The results showed that the MgO and MgO–spinel crucibles form MgO-containing inclusions(Al–Mg oxides and Al–Mg–Ti oxides),whereas the inclusions formed when using the Al2O3 crucible are Al2O3 and Al–Ti oxides.We observed a new MgAl2O4 phase at the inner wall of the MgO crucible,with the alloy melted in the MgO crucible exhibiting fewer inclusions.No new phase occurred at the inner wall of the Al2O3 crucible.We discuss the mechanism of interaction between the refractories and the Ni-based superalloy.Physical erosion was found to predominate in the Al2O3 crucible,whereas dissolution and chemical reactions dominated in the MgO crucible.No reaction was observed between three crucibles and the Ti of the melt although the Ti content(3.8wt%)was higher than that of Al(2.1wt%).展开更多
In order to improve the strength of short carbon fibers reinforced aluminum matrix(Csf/Al)composite,the dispersion of short carbon fibers with multi-orientation was controlled with a square crucible by mechanical stir...In order to improve the strength of short carbon fibers reinforced aluminum matrix(Csf/Al)composite,the dispersion of short carbon fibers with multi-orientation was controlled with a square crucible by mechanical stirring.The three-dimensional flow field models of liquid aluminum melt in the square/round crucibles were established and calculated,and the results were compared.The calculated results show that turbulent flow could be induced both in the square and round crucible,while the non-axisymmetric structure of the square crucible results in higher turbulent kinetic energy in the melt.Therefore,the uniformity and multi-orientation dispersion of the short fibers can be improved by the intensive turbulent flow in the square crucible,which will be increased by increasing the rotational velocity.The distribution of the short carbon fibers in the aluminum matrix prepared under different rotation velocities in square crucible was experimentally investigated.With the increase of stirring velocity,the multi-orientation dispersion of the short fibers in the composites increased gradually.The experimental results are consistent with the calculation results.The tensile testing results show that the strength of the Csf/Al composite can reach 172 MPa when the rotational velocity is 1000 rpm,and it is 48.3%higher than that prepared by the round crucible under the same conditions,which results from the improved multi-orientation dispersion of short carbon fibers in aluminum matrix.展开更多
The Y2O3 crucibles were introduced in the study as an alternative to the traditional ceramic ones in vacuum induction melting of multi-component Nb-16Si-22Ti-2AI-2Hf-17Cr （at.%） alloys, to reveal the possible intera...The Y2O3 crucibles were introduced in the study as an alternative to the traditional ceramic ones in vacuum induction melting of multi-component Nb-16Si-22Ti-2AI-2Hf-17Cr （at.%） alloys, to reveal the possible interactions between the alloy melt and the refractory crucible. Multiple melting time lengths and two cooling schemes were designed and used for the experiments. The chemical composition and microstructure of the tested alloy and the melt-crucible interaction were investigated and evaluated. In the experiments,Y2O3 crucible displays good physical-chemical compatibility. The results indicate that the increment of O element in the as-cast ingot iS： 0.03at.%-0.04at.% （72-97 ppm） and the increment of Y element is very insignificant. The key features of the alloy melt interacting with Y2O3 ceramics are analyzed and concluded in the paper. As a result of the dissolution reactiofi xY2O3 （in molten alloy） ＋ （1-x）HfO2 （impurity） →,Hf1-xY2xO2-x, a continuous double-layer solid film consisted of HfO2 solid solution （-2 pm） and pure HfO2 （-5μm） is formed on the surface of the test ingot after cooled down in the crucible. The experimental results show that theY2O3 crucible is applicable to the vacuum induction melting of Nb＇ Si based alloys.展开更多
To investigate the interaction mechanism between 95 Cr saw-wire steel and different refractories,we conducted laboratory experiments at 1873 K.Five crucible materials(SiO2,Al2 O3,MgO·Al2 O3,MgO,and MgO-CaO)were u...To investigate the interaction mechanism between 95 Cr saw-wire steel and different refractories,we conducted laboratory experiments at 1873 K.Five crucible materials(SiO2,Al2 O3,MgO·Al2 O3,MgO,and MgO-CaO)were used.The results indicate that SiO2,Al2 O3,and MgO·Al2 O3 are not suitable for smelting low-oxygen,low-[Al]s 95 Cr saw-wire steel,mainly because they react with the elements in the molten steel and pollute the steel samples.By contrast,MgO-CaO is an ideal choice to produce 95 Cr saw-wire steel.It offers three advantages:(ⅰ)It does not decompose by itself at the steelmaking temperature of 1873 K because it exhibits good thermal stability;(ⅱ)[C],[Si],and[Mn]in molten steel cannot react with it to increase the[O]content;and(ⅲ)it not only desulfurizes and dephosphorizes but also removes Al2 O3 inclusions from the steel simultaneously.As a result,the contents of the main elements([C],[Si],[Mn],[Cr],N,T.O(total oxygen))in the steel are not affected and the content of impurity elements([Al]s,P,and S)can be perfectly controlled within the target range.Furthermore,the number and size of inclusions in the steel samples decrease sharply when the MgO-CaO crucible is used.展开更多
文摘Experimental studies on the melting process of titanium aluminum alloy have been pursued from the viewpoint of contamination.TiAl alloys were prepared with vacuum induction melting （VIM） in calcia crucibles at 1873 K and 1923 K in order to determine the behavior of the oxygen content as a function of temperature,time and frequency of power.The experiment results showed that alloys were uncontaminated except for the increasing of oxygen content which was introduced from the reaction CaO（s）=Ca（in TiAl）＋O（in TiAl）,and the standard Gibbs energy of the reaction was determined to be △G0 =274000 102.8T（J/mol）.Oxygen content increased slowly with the melting time by about 50×10-6 wt pct/min,and decreased with induction melting frequency.Lower superheat and higher melting frequency can be used to reduce oxygen content increasing rate.
文摘The influence of crucible and vacuum on oxygen content of CuCr25 prepared by vacuum induction melting (VIM) has been investigated. The experimental results show that the selection of crucible is very important. Alkaline oxide MgO crucible can result in increment of oxygen content and segregation of Cr in the CuCr25 alloys prepared. Neutral oxide Al 2O 3 crucible has no contribution to oxygen in CuCr25. The results also indicate that some kinds of deoxidant, such as Al, are further beneficial to deoxidization of the alloys. [
基金This work is financially supported by the Natural Science Foundation of China(No.51974029)the Natural Science and Technology Major Project(No.2017-VI-0014-0086)and Fundamental Research Funds for the Central Universities(Nos.FRF-AT-19-013 and FRF-NP-19-003).
文摘This study documents laboratory-scale observation of the interactions between the Ni-based superalloy FGH4096 and refractories.Three different crucibles were tested—MgO,Al2O3,and MgO–spinel.We studied the variations in the compositions of the inclusions and the alloy–crucible interface with the reaction time using scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and Xray diffraction.The results showed that the MgO and MgO–spinel crucibles form MgO-containing inclusions(Al–Mg oxides and Al–Mg–Ti oxides),whereas the inclusions formed when using the Al2O3 crucible are Al2O3 and Al–Ti oxides.We observed a new MgAl2O4 phase at the inner wall of the MgO crucible,with the alloy melted in the MgO crucible exhibiting fewer inclusions.No new phase occurred at the inner wall of the Al2O3 crucible.We discuss the mechanism of interaction between the refractories and the Ni-based superalloy.Physical erosion was found to predominate in the Al2O3 crucible,whereas dissolution and chemical reactions dominated in the MgO crucible.No reaction was observed between three crucibles and the Ti of the melt although the Ti content(3.8wt%)was higher than that of Al(2.1wt%).
基金supported financially by the Innovation Team Project of Liaoning Province(No.LT2015020)the Special Professor Project in Liaoning Province.
文摘In order to improve the strength of short carbon fibers reinforced aluminum matrix(Csf/Al)composite,the dispersion of short carbon fibers with multi-orientation was controlled with a square crucible by mechanical stirring.The three-dimensional flow field models of liquid aluminum melt in the square/round crucibles were established and calculated,and the results were compared.The calculated results show that turbulent flow could be induced both in the square and round crucible,while the non-axisymmetric structure of the square crucible results in higher turbulent kinetic energy in the melt.Therefore,the uniformity and multi-orientation dispersion of the short fibers can be improved by the intensive turbulent flow in the square crucible,which will be increased by increasing the rotational velocity.The distribution of the short carbon fibers in the aluminum matrix prepared under different rotation velocities in square crucible was experimentally investigated.With the increase of stirring velocity,the multi-orientation dispersion of the short fibers in the composites increased gradually.The experimental results are consistent with the calculation results.The tensile testing results show that the strength of the Csf/Al composite can reach 172 MPa when the rotational velocity is 1000 rpm,and it is 48.3%higher than that prepared by the round crucible under the same conditions,which results from the improved multi-orientation dispersion of short carbon fibers in aluminum matrix.
文摘The Y2O3 crucibles were introduced in the study as an alternative to the traditional ceramic ones in vacuum induction melting of multi-component Nb-16Si-22Ti-2AI-2Hf-17Cr （at.%） alloys, to reveal the possible interactions between the alloy melt and the refractory crucible. Multiple melting time lengths and two cooling schemes were designed and used for the experiments. The chemical composition and microstructure of the tested alloy and the melt-crucible interaction were investigated and evaluated. In the experiments,Y2O3 crucible displays good physical-chemical compatibility. The results indicate that the increment of O element in the as-cast ingot iS： 0.03at.%-0.04at.% （72-97 ppm） and the increment of Y element is very insignificant. The key features of the alloy melt interacting with Y2O3 ceramics are analyzed and concluded in the paper. As a result of the dissolution reactiofi xY2O3 （in molten alloy） ＋ （1-x）HfO2 （impurity） →,Hf1-xY2xO2-x, a continuous double-layer solid film consisted of HfO2 solid solution （-2 pm） and pure HfO2 （-5μm） is formed on the surface of the test ingot after cooled down in the crucible. The experimental results show that theY2O3 crucible is applicable to the vacuum induction melting of Nb＇ Si based alloys.
基金support from the National Key Research and Development Program of China(No.2016YFB0300105)the Transformation Project of Major Scientific and Technological Achievements in Shenyang(No.Z17-5-003)the Fundamental Research Funds for the Central Universities(No.N172507002)。
文摘To investigate the interaction mechanism between 95 Cr saw-wire steel and different refractories,we conducted laboratory experiments at 1873 K.Five crucible materials(SiO2,Al2 O3,MgO·Al2 O3,MgO,and MgO-CaO)were used.The results indicate that SiO2,Al2 O3,and MgO·Al2 O3 are not suitable for smelting low-oxygen,low-[Al]s 95 Cr saw-wire steel,mainly because they react with the elements in the molten steel and pollute the steel samples.By contrast,MgO-CaO is an ideal choice to produce 95 Cr saw-wire steel.It offers three advantages:(ⅰ)It does not decompose by itself at the steelmaking temperature of 1873 K because it exhibits good thermal stability;(ⅱ)[C],[Si],and[Mn]in molten steel cannot react with it to increase the[O]content;and(ⅲ)it not only desulfurizes and dephosphorizes but also removes Al2 O3 inclusions from the steel simultaneously.As a result,the contents of the main elements([C],[Si],[Mn],[Cr],N,T.O(total oxygen))in the steel are not affected and the content of impurity elements([Al]s,P,and S)can be perfectly controlled within the target range.Furthermore,the number and size of inclusions in the steel samples decrease sharply when the MgO-CaO crucible is used.
