Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . ...Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . An i m portant reason of high abrasion resistance is hard ness violentincreasing on the m atrix surface because of w ear easily induced m artensite transfor m ation . The exploitation and applications of m etastable austenite m atrix wear alloys of Fe C Cr Nisyste m and Fe C Cr Mn system were described in this paper . The excellent properties of thesealloys w ill be sufficiently indicated by authors’exa m ples . To exploit a class of these alloyswith high abrasion resistance and various im pact toughness for m eeting the requirem ent of dif ferent environ ment , the proble m of the structure design of metastable austenite m atrix wearalloy w as also described in this paper .展开更多
A model has been developed to describe the microstructure evolution in the atomized droplets of Cu-Fe alloy during cooling through the metastable miscibility gap. Calculations have been performed for Cu85Fe15 alloy to...A model has been developed to describe the microstructure evolution in the atomized droplets of Cu-Fe alloy during cooling through the metastable miscibility gap. Calculations have been performed for Cu85Fe15 alloy to investigate the process of liquid-liquid phase transformation. The numerical results indicate that the minority phase droplets are nucleated in a temperature region around the peak of the supersaturation. The average radius of the Fe-rlch droplets decreases and the number density of the minority phase droplets increases with decreasing the atomized droplet size. The simulated results were compared with the experimental ones. The kinetic process of the liquid-liquid phase transformation was discussed in detail.展开更多
The non-equilibrium microstructure and a new metastable phase of Al-9.6wt%Mg alloy solidified at 6 GPa were studied by optical microscope,differential scanning calorimetry,X-ray diffraction and transmission electron m...The non-equilibrium microstructure and a new metastable phase of Al-9.6wt%Mg alloy solidified at 6 GPa were studied by optical microscope,differential scanning calorimetry,X-ray diffraction and transmission electron microscope.The results showed that dendrite microstructure was refined,and the solid solubility of Mg in α-Al phase increased greatly.Correspondingly,the lattice parameter of α-Al phase increased.Al3Mg2 phases disappeared under high pressure solidification.In particular,a metastable phase with small size(20 nm or so) was produced in the alloy,its melting temperature range was 464～518.2 ℃,which was higher than that of Al3Mg2 phase(453～465 ℃) under normal pressure.These metastable phases located in the interdendritic position.It was the first time that the metastable phase was found in Al-Mg alloy at a high pressure of 6 GPa.The formation mechanism of the metastable phases was discussed.展开更多
The precipitation behaviour of Fe-Cr-Mo and Fe-Cr-W alloys during aging has been ex- perimentally studied.It was found that in the early stage of aging,a metastable R phase pre- cipitated in both alloys,it was transfo...The precipitation behaviour of Fe-Cr-Mo and Fe-Cr-W alloys during aging has been ex- perimentally studied.It was found that in the early stage of aging,a metastable R phase pre- cipitated in both alloys,it was transformed into stable μ-phase,Laves-phase,X-phase or σ-phase in the later stages.The crystallographic structure of metastable R-phase is rhombohedral with lattice parameters of a=0.9075 nm and α=74.45°.The chemical compo- sition of R-phase is Fe-(27.5—34.9)Mo-(0—25.5)Cr and Fe-(28.9—33.0)W-(9.36— 21.0)Cr in at.-% in Fe-Cr-Mo and Fe-Cr-W system,respectively.展开更多
In order to clarify that the IFP and the “Type 2”α phase are also arising from TiC,a metastable β-Ti alloy was selected for investigation in this work.The results showed that af- ter heating the alloy just below t...In order to clarify that the IFP and the “Type 2”α phase are also arising from TiC,a metastable β-Ti alloy was selected for investigation in this work.The results showed that af- ter heating the alloy just below the α+β→β transus temperature and quenching,the TiC lay- er existed at the α/β interface.The morphology of TiC is similar to that of the IFP arising from TiH_2 in the α-β two-phase alloys.The IFP TiC also provided an easy crack path or the crack initiation sites.The fracture is also identical to that caused by IFP TiH_2.The arced diffractions(characteristic of “Type 2”α)were found in the selected area diffraction pat- terns of some specimens which had been isothermally aged after solid solution treatment.The particles which bring on the arced diffractions may be TiC on the basis of structure and lat- tice parameter analysis,not the so called “Type 2”α phase.展开更多
The splat foils of Al-Sm alloys with 0.04-0.06mm in thickness were made by hammeranvil technique. The estimated cooling rute was 106K/ order of magnitude. The extended solid solubility of Sm in α-Al reached 0.5at. % ...The splat foils of Al-Sm alloys with 0.04-0.06mm in thickness were made by hammeranvil technique. The estimated cooling rute was 106K/ order of magnitude. The extended solid solubility of Sm in α-Al reached 0.5at. % Sm. The intermediate phase in the rapidlysolidified Al-Sm alloys is Al11Sm3 phase, which is stable only at temperatures above 1339K in equilibrium state and retained to ambient temperature as a metastable phase, whereas the equlibrium intermediate phase, Al3Sm, was restricted to occur.展开更多
Pattern recognition and neural network methods have been used to investigate the formability of metastable alloy phases, It has been found that some chemi cal bond parameters Such as valence electron number, electrone...Pattern recognition and neural network methods have been used to investigate the formability of metastable alloy phases, It has been found that some chemi cal bond parameters Such as valence electron number, electronegativity and metallic radii of cor-nponent elements are the dominating fac tors affecting metastable alloy phase formation. Some semi-empirical rules found in this way may be useful for the construction of expert system for materials design.展开更多
Mechanical alloying (MA) was applied to Ag B immiscible binary systems by ball milling elemental Ag and B powders. The microstructural characterization of the milled powders was carried out by XRD and TEM. The results...Mechanical alloying (MA) was applied to Ag B immiscible binary systems by ball milling elemental Ag and B powders. The microstructural characterization of the milled powders was carried out by XRD and TEM. The results show that face centered cubic (FCC) Ag B solid solutions are formed and that the maximum ratio of B to Ag is 4∶1. The structure evolution of Ag B solid solution during ball milling indicates that the formation of Ag B solid solution may be divided into two stages, which are mainly substitutional and interstitial solutions separately. The decomposition of the as milled granules under the irradiation of electron beam is observed by TEM, which reveals that the solid solutions are metastable.展开更多
The precipitation process of aged Cu-Ni-Be alloy was investigated by X-ray diffraction （XRD）, trans- mission electron microscopy （TEM）, and high-resolution transmission electron microscopy （HRTEM）. The tensile s...The precipitation process of aged Cu-Ni-Be alloy was investigated by X-ray diffraction （XRD）, trans- mission electron microscopy （TEM）, and high-resolution transmission electron microscopy （HRTEM）. The tensile strength, yield strength, and electronic conductivity of this alloy after aging were also studied. The precipitation sequence of the C17510 alloy aged at 525 ℃ is supersat-urated solid solution→G.P zones→ γ″-γ′→ γ. This transformation can be achieved by the accumulation of Be-atom layers. The G.P zones are composed of disk-shaped monolayers of Be atoms, which are formed on （001） matrix planes. The intermediate γ″ precipitate is nucleated in the G.P zones. The γ″ and γ′ precipitates have the same orientation relationship with matrix, e.g., （110）p｜｜（100）M,[001]p｜｜[001]M. The tensile strength of specimen shows a maximum during the aging process and then continuously decreases if the specimen is over aged. The strengthening effect of γ′ phase precipitated in aging at 525 ℃ for 4 h is calculated to be 436 MPa according to the Orowan strengthening, which is quite consistent with the experimental data.展开更多
The dynamics of phase separation of CuCo alloys has been studied by numerically solving the nonlinear Cahn-Hilliard equation including thermal noises.The simulations show that phase separation of the alloys within the...The dynamics of phase separation of CuCo alloys has been studied by numerically solving the nonlinear Cahn-Hilliard equation including thermal noises.The simulations show that phase separation of the alloys within the metastable region is attributed to the composition fluctuations including thermal noises.The present modeling makes it possible to describe the growth and coarsening as concomitant processes.展开更多
The quench transfomation in a Ti-10V-2Fe-3Al near B-titanium alloy was studied by means of X-ray diffraction, transmission electron microscopy, and optical micyoscopy. The quenching temperatures were above and below t...The quench transfomation in a Ti-10V-2Fe-3Al near B-titanium alloy was studied by means of X-ray diffraction, transmission electron microscopy, and optical micyoscopy. The quenching temperatures were above and below the β transus temperature. The phase constitutions of specimens quenched from various solution temperatures were identified and the phase morphologies were examined. In addition, the relationship between phase lattice parameters and quenching tempera- tures was given for α, β and α ^(11) phases. This alloy has a tendency of precipitation of athermal ω phase and formation of stress induced α^(11) mar- tensite from β phase during quenching. Quenched from the temperatures above the β transus tem- perature, the alloy mainly consists of β phase, a small amount of α^(11) martensite and athemal ω phase aye also present in the alloy. After quenching from the temperatures below the β transus temperature, the α phase appeays in the alloy in addition to the phases mentioned above.展开更多
The high undercooling technique by molten glass slag purification and cyclical superheating in Ar atmosphere was applied to bulk Fe-B alloy melts. A hypercooling was achieved which suppressed the formation of stable p...The high undercooling technique by molten glass slag purification and cyclical superheating in Ar atmosphere was applied to bulk Fe-B alloy melts. A hypercooling was achieved which suppressed the formation of stable phase and consequently promoted the nucleation of metastable phase. Fe-17%B and Fe-20%B alloys were investigated, respectively. TEM and X-ray powder diffraction analyses verify the formation of metastable phase in the highly undercooled Fe-B alloy melts. Besides, the critical nucleation work of Fe2B and Fe3B phases was calculated to predict phase selection in the undercooled melts. The results show that the metastable phase formation is a function of the undercooling achieved prior to nucleation. And the amount of undercooling is an important factor in determining microstructural development by controlling phase selection in the undercooled melts.展开更多
Rapidly solidified Al 8.4Fe 1.3V 1.7Si heat resistant alloy was made by using multi layer spray deposition technique. Its thermal stability of mechanical properties was investigated by the means of tensile and hardnes...Rapidly solidified Al 8.4Fe 1.3V 1.7Si heat resistant alloy was made by using multi layer spray deposition technique. Its thermal stability of mechanical properties was investigated by the means of tensile and hardness tests, thermal stability of microstructure by transmission electron microscopy (TEM), X ray diffraction (XRD). The results show that after heat exposure (HE) at 753?K for 500?h the tensile strength and hardness of Al Fe V Si alloy at 623?K maintains the same values as those at room temperature. HE dose not obviously affect the thermal stabilities of Al 12 (Fe,V) 3Si phase but the lattice constant of Al 12 (Fe,V) 3Si phase decrease.展开更多
文摘Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . An i m portant reason of high abrasion resistance is hard ness violentincreasing on the m atrix surface because of w ear easily induced m artensite transfor m ation . The exploitation and applications of m etastable austenite m atrix wear alloys of Fe C Cr Nisyste m and Fe C Cr Mn system were described in this paper . The excellent properties of thesealloys w ill be sufficiently indicated by authors’exa m ples . To exploit a class of these alloyswith high abrasion resistance and various im pact toughness for m eeting the requirem ent of dif ferent environ ment , the proble m of the structure design of metastable austenite m atrix wearalloy w as also described in this paper .
基金the finan cial supports from the National Natural Science Foundation of China(Grant Nos.50271076,50371092 , 50395104)the Sino-Germany Science Foundation(GZ032/1) the Natural Science Foundation of Liaoning Province of China.
文摘A model has been developed to describe the microstructure evolution in the atomized droplets of Cu-Fe alloy during cooling through the metastable miscibility gap. Calculations have been performed for Cu85Fe15 alloy to investigate the process of liquid-liquid phase transformation. The numerical results indicate that the minority phase droplets are nucleated in a temperature region around the peak of the supersaturation. The average radius of the Fe-rlch droplets decreases and the number density of the minority phase droplets increases with decreasing the atomized droplet size. The simulated results were compared with the experimental ones. The kinetic process of the liquid-liquid phase transformation was discussed in detail.
基金This work is financially supported by the Science Foundation of Harbin Institute of Technology ( No HIT2002 29)
文摘The non-equilibrium microstructure and a new metastable phase of Al-9.6wt%Mg alloy solidified at 6 GPa were studied by optical microscope,differential scanning calorimetry,X-ray diffraction and transmission electron microscope.The results showed that dendrite microstructure was refined,and the solid solubility of Mg in α-Al phase increased greatly.Correspondingly,the lattice parameter of α-Al phase increased.Al3Mg2 phases disappeared under high pressure solidification.In particular,a metastable phase with small size(20 nm or so) was produced in the alloy,its melting temperature range was 464～518.2 ℃,which was higher than that of Al3Mg2 phase(453～465 ℃) under normal pressure.These metastable phases located in the interdendritic position.It was the first time that the metastable phase was found in Al-Mg alloy at a high pressure of 6 GPa.The formation mechanism of the metastable phases was discussed.
文摘The precipitation behaviour of Fe-Cr-Mo and Fe-Cr-W alloys during aging has been ex- perimentally studied.It was found that in the early stage of aging,a metastable R phase pre- cipitated in both alloys,it was transformed into stable μ-phase,Laves-phase,X-phase or σ-phase in the later stages.The crystallographic structure of metastable R-phase is rhombohedral with lattice parameters of a=0.9075 nm and α=74.45°.The chemical compo- sition of R-phase is Fe-(27.5—34.9)Mo-(0—25.5)Cr and Fe-(28.9—33.0)W-(9.36— 21.0)Cr in at.-% in Fe-Cr-Mo and Fe-Cr-W system,respectively.
文摘In order to clarify that the IFP and the “Type 2”α phase are also arising from TiC,a metastable β-Ti alloy was selected for investigation in this work.The results showed that af- ter heating the alloy just below the α+β→β transus temperature and quenching,the TiC lay- er existed at the α/β interface.The morphology of TiC is similar to that of the IFP arising from TiH_2 in the α-β two-phase alloys.The IFP TiC also provided an easy crack path or the crack initiation sites.The fracture is also identical to that caused by IFP TiH_2.The arced diffractions(characteristic of “Type 2”α)were found in the selected area diffraction pat- terns of some specimens which had been isothermally aged after solid solution treatment.The particles which bring on the arced diffractions may be TiC on the basis of structure and lat- tice parameter analysis,not the so called “Type 2”α phase.
文摘The splat foils of Al-Sm alloys with 0.04-0.06mm in thickness were made by hammeranvil technique. The estimated cooling rute was 106K/ order of magnitude. The extended solid solubility of Sm in α-Al reached 0.5at. % Sm. The intermediate phase in the rapidlysolidified Al-Sm alloys is Al11Sm3 phase, which is stable only at temperatures above 1339K in equilibrium state and retained to ambient temperature as a metastable phase, whereas the equlibrium intermediate phase, Al3Sm, was restricted to occur.
文摘Pattern recognition and neural network methods have been used to investigate the formability of metastable alloy phases, It has been found that some chemi cal bond parameters Such as valence electron number, electronegativity and metallic radii of cor-nponent elements are the dominating fac tors affecting metastable alloy phase formation. Some semi-empirical rules found in this way may be useful for the construction of expert system for materials design.
基金Acknowledgment： This work was financially supported by the Natural Science Foundation of China （No. 50661001 and 50061001） and the Science Foundation of Guangxi Province （No. 0832029 and 0639004）.
文摘Mechanical alloying (MA) was applied to Ag B immiscible binary systems by ball milling elemental Ag and B powders. The microstructural characterization of the milled powders was carried out by XRD and TEM. The results show that face centered cubic (FCC) Ag B solid solutions are formed and that the maximum ratio of B to Ag is 4∶1. The structure evolution of Ag B solid solution during ball milling indicates that the formation of Ag B solid solution may be divided into two stages, which are mainly substitutional and interstitial solutions separately. The decomposition of the as milled granules under the irradiation of electron beam is observed by TEM, which reveals that the solid solutions are metastable.
基金financially supported by the Project of Science and Technology of Beijing(No.10231103)
文摘The precipitation process of aged Cu-Ni-Be alloy was investigated by X-ray diffraction （XRD）, trans- mission electron microscopy （TEM）, and high-resolution transmission electron microscopy （HRTEM）. The tensile strength, yield strength, and electronic conductivity of this alloy after aging were also studied. The precipitation sequence of the C17510 alloy aged at 525 ℃ is supersat-urated solid solution→G.P zones→ γ″-γ′→ γ. This transformation can be achieved by the accumulation of Be-atom layers. The G.P zones are composed of disk-shaped monolayers of Be atoms, which are formed on （001） matrix planes. The intermediate γ″ precipitate is nucleated in the G.P zones. The γ″ and γ′ precipitates have the same orientation relationship with matrix, e.g., （110）p｜｜（100）M,[001]p｜｜[001]M. The tensile strength of specimen shows a maximum during the aging process and then continuously decreases if the specimen is over aged. The strengthening effect of γ′ phase precipitated in aging at 525 ℃ for 4 h is calculated to be 436 MPa according to the Orowan strengthening, which is quite consistent with the experimental data.
基金supported by the National High Technology Research and Development Program of China (No. 2011AA030101)the State Key Laboratory for Mechanical Behavior of Materials (No. 201011007)the Key Science and Technology Special Project of Shaanxi Province (No. 2009ZKC03-16)
基金Supported by the National Natural Science Foundation of China.
文摘The dynamics of phase separation of CuCo alloys has been studied by numerically solving the nonlinear Cahn-Hilliard equation including thermal noises.The simulations show that phase separation of the alloys within the metastable region is attributed to the composition fluctuations including thermal noises.The present modeling makes it possible to describe the growth and coarsening as concomitant processes.
文摘The quench transfomation in a Ti-10V-2Fe-3Al near B-titanium alloy was studied by means of X-ray diffraction, transmission electron microscopy, and optical micyoscopy. The quenching temperatures were above and below the β transus temperature. The phase constitutions of specimens quenched from various solution temperatures were identified and the phase morphologies were examined. In addition, the relationship between phase lattice parameters and quenching tempera- tures was given for α, β and α ^(11) phases. This alloy has a tendency of precipitation of athermal ω phase and formation of stress induced α^(11) mar- tensite from β phase during quenching. Quenched from the temperatures above the β transus tem- perature, the alloy mainly consists of β phase, a small amount of α^(11) martensite and athemal ω phase aye also present in the alloy. After quenching from the temperatures below the β transus temperature, the α phase appeays in the alloy in addition to the phases mentioned above.
基金Projects(50395103 50271057 50501020) supported by the National Natural Science Foundation of China
文摘The high undercooling technique by molten glass slag purification and cyclical superheating in Ar atmosphere was applied to bulk Fe-B alloy melts. A hypercooling was achieved which suppressed the formation of stable phase and consequently promoted the nucleation of metastable phase. Fe-17%B and Fe-20%B alloys were investigated, respectively. TEM and X-ray powder diffraction analyses verify the formation of metastable phase in the highly undercooled Fe-B alloy melts. Besides, the critical nucleation work of Fe2B and Fe3B phases was calculated to predict phase selection in the undercooled melts. The results show that the metastable phase formation is a function of the undercooling achieved prior to nucleation. And the amount of undercooling is an important factor in determining microstructural development by controlling phase selection in the undercooled melts.
文摘Rapidly solidified Al 8.4Fe 1.3V 1.7Si heat resistant alloy was made by using multi layer spray deposition technique. Its thermal stability of mechanical properties was investigated by the means of tensile and hardness tests, thermal stability of microstructure by transmission electron microscopy (TEM), X ray diffraction (XRD). The results show that after heat exposure (HE) at 753?K for 500?h the tensile strength and hardness of Al Fe V Si alloy at 623?K maintains the same values as those at room temperature. HE dose not obviously affect the thermal stabilities of Al 12 (Fe,V) 3Si phase but the lattice constant of Al 12 (Fe,V) 3Si phase decrease.
