The excellent corrosion resistance,formability and strength make stainless steels versatile for diverse applications.However,its high specific strength and good crashworthiness make it suitable for transportation and ...The excellent corrosion resistance,formability and strength make stainless steels versatile for diverse applications.However,its high specific strength and good crashworthiness make it suitable for transportation and aerospace industry.On the other hand,the need to reduce the weight of vehicle and aerospace components has created renewed interest in the use of magnesium alloys.Due to their differences in physical and metallurgical properties,bonding of the 316L steel and AZ31 magnesium alloy using conventional fusion welding methods encountered many limitations.Therefore,the use of liquid phase forming interlayers is required to overcome the differences in their properties,eliminates the need for a high bonding pressure to achieve intimate contact between the bonded surfaces.Both Cu and Ni interlayers successively formed a eutectic phase with magnesium.The formation of intermetallics and Mg diffusion caused the eutectic phase to isothermally solidify with increasing bonding time.The formation of ternary intermetallic phases（λ1 and B2） impaired the bond shear strength particularly at the end of the isothermal solidification stage where no eutectic phase was observed.However,the joints showed a higher shear strength value of 57 MPa when bonding with Cu interlayer at 530℃ for 30 min compared to 32 MPa when Ni interlayer was used at 510℃ for 20 min.展开更多
The effect of rare earths on the morphology and microstructure of eutectic carbides in M2 high speed steel was studied. The results showed that rare earths promoted the forrmation of fishbone-like M6C eutectic carbide...The effect of rare earths on the morphology and microstructure of eutectic carbides in M2 high speed steel was studied. The results showed that rare earths promoted the forrmation of fishbone-like M6C eutectic carbides, compared to plate-like M2C carbides in ingots without modification. The formation of M6C was expected to be caused by rare earth inclusions which acted effectively as the substratc for nucleation of M6C carbides during solidification. M2C and M6C eutectic carbides exhibited different stability during heating. M2C eutectic carbides were much less stable than M6C carbides, and decomposed at high temperatures, favoring the spheroidization and refmement of carbides inhigh speed steels.展开更多
Laser 3D printing based on melt growth has great potential in rapid preparation of Al_(2)O_(3)-based eutectic ce ramics.In this work,la rge-scale Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)ternary eutectic ceramic rod with diameter...Laser 3D printing based on melt growth has great potential in rapid preparation of Al_(2)O_(3)-based eutectic ce ramics.In this work,la rge-scale Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)ternary eutectic ceramic rod with diameter of 4-5 mm and height higher than 250 mm was additively manufactured by laser directed energy deposition.Especially,heat treatment was applied to eliminate the microstructure heterogeneity in the as-deposited eutectic ceramic,and the microstructure homogenization mechanism was studied in depth.The results indicate that colonies and banded structures completely disappear after the heat treatment,producing a homogeneous network eutectic structure.The microstructure homogenization is revealed to experience three stages of discontinuous coarsening,continuous coarsening and microstructure coalescence.Additionally,it is found that the eutectic spacing linearly increases with the heat treatment time,meaning that the coarsening behavior of the laser 3D-printed Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)eutectic ceramic satisfies well with the Graham-Kraft model.展开更多
In this work,we demonstrate that the corrosion resistance of the FeCrNiCoNb_(0.5) eutectic high entropy alloy(EHEA)can be tuned by controlling the size of its eutectic structure.Through microstructure refinement,the E...In this work,we demonstrate that the corrosion resistance of the FeCrNiCoNb_(0.5) eutectic high entropy alloy(EHEA)can be tuned by controlling the size of its eutectic structure.Through microstructure refinement,the EHEA exhibits a superb corrosion resistance in 1 M NaCl in terms of a very low corrosion current density and an ultra-high transpassviation potential,which outperforms a variety of other HEAs and conventional metals and alloys.At the fundamental level,the microstructure refinement results in a rapid formation of a thick and compact passive film with less Cl-adsorption on the EHEA,which results in significant enhancement in its corrosion resistance.The outcome of our research provides important insights into the design of corrosion resistant chemically complex alloys.展开更多
The effects of Ga on microstructures and mechanical properties of the cadmium-free silver based brazing filler metals have been investigated. The results indicated that C,a additions had the noticeable effect on the m...The effects of Ga on microstructures and mechanical properties of the cadmium-free silver based brazing filler metals have been investigated. The results indicated that C,a additions had the noticeable effect on the microstructure, especially on the shape of the phases. With the increase of Ga addition, the amount of eutectic structure increased, and the acicular eutectic structure changed into the fine eutectic structure with micro-vermiform and rod-like shape. When the addition of Ga was 3.0 wt. %, none of defects exist in the microstructure of the brazed joint. The tensile strength increased from 382 MPa to 511 MPa with the content of Ga increasing from 0 to 3.0 wt. %.展开更多
Low-melting-point alloys have an extensive applications in the fields of materials processing, phase change energy storage, electronic and electrical automatic control, continuous casting simulation, welding, etc. Spe...Low-melting-point alloys have an extensive applications in the fields of materials processing, phase change energy storage, electronic and electrical automatic control, continuous casting simulation, welding, etc. Specifically, the eutectic compositions make up a large number of low-melting-point alloys that are ex- ploited because of their desirable features like single melting peaks, excellent operational reliability, and casting fluidity. However, the fundamental physicochemical properties from the current available liter- ature on low-melting-point multi-component eutectic alloys （LMP-MCEAs） are rather rare and lowly accurate, including the exact melting temperatures and compositions, constituent phases, microstruc- tures and morphologies, melting enthalpies, specific heats, densities, and so on. This lack of information seriously limits the development and application of low-melting-point multi-component eutectic alloys. In this paper, the low-melting-point multi-component eutectic alloys composed of Bi, Cd, Sn, Pb, and In elements synthesized by high vacuum induction melting and fundamental data were investigated by scan- ning electron microscopy （SEM）, energy dispersive spectrometry （EDS）, X-ray diffraction （XRD）, differential scanning calorimetry （DSC）, and density analysis instrument. Most of the LMP-MCEAs with complex eu- tectic morphology structures and XRD diffraction patterns could be explained with the fact that they were three-phase eutectic alloys with mixed growth way. Generally, LMP-MCEAs present an extremely low melting point between 48.3 and 124 ℃ and high density between 8 and 10 g/cm3.展开更多
基金the EMOD,EAA and MTC Egypt for sponsoring this work
文摘The excellent corrosion resistance,formability and strength make stainless steels versatile for diverse applications.However,its high specific strength and good crashworthiness make it suitable for transportation and aerospace industry.On the other hand,the need to reduce the weight of vehicle and aerospace components has created renewed interest in the use of magnesium alloys.Due to their differences in physical and metallurgical properties,bonding of the 316L steel and AZ31 magnesium alloy using conventional fusion welding methods encountered many limitations.Therefore,the use of liquid phase forming interlayers is required to overcome the differences in their properties,eliminates the need for a high bonding pressure to achieve intimate contact between the bonded surfaces.Both Cu and Ni interlayers successively formed a eutectic phase with magnesium.The formation of intermetallics and Mg diffusion caused the eutectic phase to isothermally solidify with increasing bonding time.The formation of ternary intermetallic phases（λ1 and B2） impaired the bond shear strength particularly at the end of the isothermal solidification stage where no eutectic phase was observed.However,the joints showed a higher shear strength value of 57 MPa when bonding with Cu interlayer at 530℃ for 30 min compared to 32 MPa when Ni interlayer was used at 510℃ for 20 min.
基金Project supported by Fund of Transformation of Scientific and Technological Achievements from Jiangsu Province(BA2010139)the Opening Project of Jiangsu Key Laboratory of Advanced Metallic Materials(AMM201203)
文摘The effect of rare earths on the morphology and microstructure of eutectic carbides in M2 high speed steel was studied. The results showed that rare earths promoted the forrmation of fishbone-like M6C eutectic carbides, compared to plate-like M2C carbides in ingots without modification. The formation of M6C was expected to be caused by rare earth inclusions which acted effectively as the substratc for nucleation of M6C carbides during solidification. M2C and M6C eutectic carbides exhibited different stability during heating. M2C eutectic carbides were much less stable than M6C carbides, and decomposed at high temperatures, favoring the spheroidization and refmement of carbides inhigh speed steels.
基金financially supported by the National Key R&D Program of China(Nos.2018YFB1106600 and 2017YFB1103500)Science,Technology and Innovation Commission of Shenzhen Municipality(No.JCYJ20180306171121424)+4 种基金National Natural Science Foundation of China(Nos.51822405,51472200)Aeronautics Power Foundation(No.6141B09050337)Key R&D Program of Shaan Xi Province(No.2018ZDCXL-GY-09-04)Joint Research Funds of the Department of Science&Technology of Shaanxi Province and NPU(No.2020GXLH-Z-024)Research Fund of the State Key Laboratory of Solidification Processing(NPU)(No.2019QZ-02)。
文摘Laser 3D printing based on melt growth has great potential in rapid preparation of Al_(2)O_(3)-based eutectic ce ramics.In this work,la rge-scale Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)ternary eutectic ceramic rod with diameter of 4-5 mm and height higher than 250 mm was additively manufactured by laser directed energy deposition.Especially,heat treatment was applied to eliminate the microstructure heterogeneity in the as-deposited eutectic ceramic,and the microstructure homogenization mechanism was studied in depth.The results indicate that colonies and banded structures completely disappear after the heat treatment,producing a homogeneous network eutectic structure.The microstructure homogenization is revealed to experience three stages of discontinuous coarsening,continuous coarsening and microstructure coalescence.Additionally,it is found that the eutectic spacing linearly increases with the heat treatment time,meaning that the coarsening behavior of the laser 3D-printed Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)eutectic ceramic satisfies well with the Graham-Kraft model.
基金supported by the Research Grant Council(RGC),Hong Kong Government,through the General Research Fund(GRF)with the grant number City U11213118 and City U11209317。
文摘In this work,we demonstrate that the corrosion resistance of the FeCrNiCoNb_(0.5) eutectic high entropy alloy(EHEA)can be tuned by controlling the size of its eutectic structure.Through microstructure refinement,the EHEA exhibits a superb corrosion resistance in 1 M NaCl in terms of a very low corrosion current density and an ultra-high transpassviation potential,which outperforms a variety of other HEAs and conventional metals and alloys.At the fundamental level,the microstructure refinement results in a rapid formation of a thick and compact passive film with less Cl-adsorption on the EHEA,which results in significant enhancement in its corrosion resistance.The outcome of our research provides important insights into the design of corrosion resistant chemically complex alloys.
文摘The effects of Ga on microstructures and mechanical properties of the cadmium-free silver based brazing filler metals have been investigated. The results indicated that C,a additions had the noticeable effect on the microstructure, especially on the shape of the phases. With the increase of Ga addition, the amount of eutectic structure increased, and the acicular eutectic structure changed into the fine eutectic structure with micro-vermiform and rod-like shape. When the addition of Ga was 3.0 wt. %, none of defects exist in the microstructure of the brazed joint. The tensile strength increased from 382 MPa to 511 MPa with the content of Ga increasing from 0 to 3.0 wt. %.
基金supported by the National Natural Science Foundation of China (Nos. 51525401 and 51471044)the Fundamental Research Funds for the Central Universities (No. DUT14LH013)+1 种基金Key Laboratory of Basic Research Projects of Liaoning Province Department of Education (No. LZ2014007)the Natural Science Foundation of Liaoning Province (No. 2014028013)
文摘Low-melting-point alloys have an extensive applications in the fields of materials processing, phase change energy storage, electronic and electrical automatic control, continuous casting simulation, welding, etc. Specifically, the eutectic compositions make up a large number of low-melting-point alloys that are ex- ploited because of their desirable features like single melting peaks, excellent operational reliability, and casting fluidity. However, the fundamental physicochemical properties from the current available liter- ature on low-melting-point multi-component eutectic alloys （LMP-MCEAs） are rather rare and lowly accurate, including the exact melting temperatures and compositions, constituent phases, microstruc- tures and morphologies, melting enthalpies, specific heats, densities, and so on. This lack of information seriously limits the development and application of low-melting-point multi-component eutectic alloys. In this paper, the low-melting-point multi-component eutectic alloys composed of Bi, Cd, Sn, Pb, and In elements synthesized by high vacuum induction melting and fundamental data were investigated by scan- ning electron microscopy （SEM）, energy dispersive spectrometry （EDS）, X-ray diffraction （XRD）, differential scanning calorimetry （DSC）, and density analysis instrument. Most of the LMP-MCEAs with complex eu- tectic morphology structures and XRD diffraction patterns could be explained with the fact that they were three-phase eutectic alloys with mixed growth way. Generally, LMP-MCEAs present an extremely low melting point between 48.3 and 124 ℃ and high density between 8 and 10 g/cm3.
