Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3 alloy has high chemical activity and favorable plateaus pressure. Mg2Ni is in favor of high hydrogen storage capacity and low weight, but it is difficult to be activated. In order to ...Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3 alloy has high chemical activity and favorable plateaus pressure. Mg2Ni is in favor of high hydrogen storage capacity and low weight, but it is difficult to be activated. In order to improve the capacity and cycle performances of hydrogen-storage alloy electrodes, Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3-x%Mg2Ni(x=0, 5, 10, 30) composite hydrogen storage alloys prepared by two-step re-melting were investigated in this work. The influences of Mg2Ni content on the cycle stabilities were analyzed by electrochemical methods. It was observed by XRD that the main phase of all the alloys is LaNi5 and the crystal lattice parameters of LaNi5 are changed with the increasing of x value, i.e, a-axis and unit cell volume decrease and c-axis decreases nonlinearly. The c-axis of alloy with x=5 is larger than the others. With the increasing of x value, capacity retentions of the composite hydrogen storage alloys rise from 66.21% while x=0 to 82.04% while x=10, but the capacity retention of the composite alloy with 30% Mg2Ni declines because of its decreasing axial ratio. More over, the composite alloy with 5% Mg2Ni shows the best cycle stability and higher discharge capacity, and it is an appropriate candidate for battery materials.展开更多
The microstructure and phase composition of as-cast Mg-9Er-6Y-xZn-0.6Zr (x=1, 2, 3, 4; normal mass fraction in %) alloys were investigated. In low Zn content, aside from the major second phase of Mg24(Er, Y, Zn)5,...The microstructure and phase composition of as-cast Mg-9Er-6Y-xZn-0.6Zr (x=1, 2, 3, 4; normal mass fraction in %) alloys were investigated. In low Zn content, aside from the major second phase of Mg24(Er, Y, Zn)5, there are a few lamellar phases that grow parallel with each other from the grain boundaries to the grain interior. With Zn content increasing, the Mg24(Er, Y, Zn)5 phase decreases, but the Mg12Zn(Y, Er) phase and lamellar phases continuously increase. When Zn content reaches 4% (normal mass fraction), the Mg12Zn(Y, Er) phase mainly exists as large bulks, and some a-Mg grains are thoroughly penetrated by the lamellar phases. Moreover, the crystallography structures of the Mgl2Zn(Y, Er) and Mg24(Er, Y, Zn)5 phases are confirmed as 18R-type long-period stacking ordered structure and body-centred cubic structure, respectively.展开更多
The general use of aluminium as an indentation standard for the iteration of contact heights for the determination of ISO-14577 hardness and elastic modulus is challenged because of as yet not appreciated phase-change...The general use of aluminium as an indentation standard for the iteration of contact heights for the determination of ISO-14577 hardness and elastic modulus is challenged because of as yet not appreciated phase-changes in the physical force-depth standard curve that seemed to be secured by claims from 1992. The physical and mathematical analyses with closed formulas avoid the still world-wide standardized energy-law violation by not reserving 33.33% (h2 belief) (or 20% h3/2 physical law) of the loading force and thus energy for all not depth producing events but using 100% for the depth formation is a severe violation of the energy law. The not depth producing part of the indentation work cannot be done with zero energy! Both twinning and structural phase-transition onsets and normalized phase-transition energies are now calculated without iterations but with physically correct closed arithmetic equations. These are reported for Berkovich and cubecorner indentations, including their comparison on geometric grounds and an indentation standard without mechanical twinning is proposed. Characteristic data are reported. This is the first detection of the indentation twinning of aluminium at room temperature and the mechanical twinning of fused quartz is also new. Their disqualification as indentation standards is established. Also, the again found higher load phase-transitions disqualify aluminium and fused quartz as ISO-ASTM 14577 (International Standardization Organization and American Society for Testing and Materials) standards for the contact depth “hc” iterations. The incorrect and still world-wide used black-box values for H- and Er-values (the latter are still falsely called “Young’s moduli” even though they are not directional) and all mechanical properties that depend on them. They lack relation to bulk moduli from compression experiments. Experimentally obtained and so published force vs depth parabolas always follow the linear FN = kh3/2 + Fa equation, where Fa is the axis-cut before and after the phase-transition branches (never “h2” as falsely enforced and used for H, Er and giving incorrectly calculated parameters). The regression slopes k are the precise physical hardness values, which for the first time allow for precise calculation of the mechanical qualities by indentation in relation to the geometry of the indenter tip. Exactly 20% of the applied force and thus energy is not available for the indentation depth. Only these scientific k-values must be used for AI-advises at the expense of falsely iterated indentation hardness H-values. Any incorrect H-ISO-ASTM and also the iterated Er-ISO-ASTM modulus values of technical materials in artificial intelligence will be a disaster for the daily safety. The AI must be told that these are unscientific and must therefore be replaced by physical data. Iterated data (3 and 8 free parameters!) cannot be transformed into physical data. One has to start with real experimental loading curves and an absolute ZerodurR standard that must be calibrated with standard force and standard length to create absolute indentation results. .展开更多
The microstructures and interface structures of basalt particle reinforced 7A04 Al matrix composites (BP/7A04 Al) were analyzed by using OM, TEM, SEM and EDS, and the mechanical properties of 7A04 Al alloy were compar...The microstructures and interface structures of basalt particle reinforced 7A04 Al matrix composites (BP/7A04 Al) were analyzed by using OM, TEM, SEM and EDS, and the mechanical properties of 7A04 Al alloy were compared with those of BP/7A04 Al matrix composites. The results show that the basalt particles are dispersed in the Al matrix and form a strong bonding interface with the Al matrix. SiO2 at the edge of the basalt particles is continuously replaced by Al2O3 formed in the reaction, forming a high-temperature reaction layer with a thickness of several tens of nanometers, and Al2O3 strengthens the bonding interface between basalt particles and Al matrix. The dispersed basalt particles promote the dislocation multiplication, vacancy formation and precipitation of the matrix, and the precipitated phases mainly consist of plate-like η(MgZn2) phase and bright white band-shaped or ellipsoidal T (Al2Mg3Zn3) phase. The bonding interface, high dislocation density and dispersion strengthening phase significantly improve the mechanical properties of the composites. The yield strength and ultimate tensile strength of BP/7A04 Al matrix composites are up to 665 and 699 MPa, which increase by 11.4% and 10.9% respectively compared with 7A04 Al alloy without basalt particles.展开更多
It was shown by TEM and X-ray analysis that there are four types of grains of the main Ni3Al phase in the structure of the intermetallic obtained by the self-propagation high temperature method (SHS). Every type of gr...It was shown by TEM and X-ray analysis that there are four types of grains of the main Ni3Al phase in the structure of the intermetallic obtained by the self-propagation high temperature method (SHS). Every type of grains has its own domain and dislocation structure. There are mono- and polydomains with and without dislocations. The grains of the main phase of monoand polydomains without dislocations and polydomains with dislocations were formed by diffusion in the solid phase. In these conditions NiAl3 phase is located on the grain boundary of the main phase. The Ni2Al3 phase is located at the triple joints of the main phase.展开更多
The effect of TiO;,ZrO;and Na;AlF;ultrafine powders on the fine structure and the phase composition of Fe–14Mn–1.2C steel was investigated.The introduction of the ultrafine powders into the melt influenced the grain...The effect of TiO;,ZrO;and Na;AlF;ultrafine powders on the fine structure and the phase composition of Fe–14Mn–1.2C steel was investigated.The introduction of the ultrafine powders into the melt influenced the grain size,the quantity,and the character of distribution of nonmetallic inclusions in the railroad frogs.The microstructure of castings was improved significantly because of the refinement of the grain structure and an increase of the grain-boundary area.After the modifying mixture was introduced into the melt,either the microtwins of one or two intersecting systems or the precipitations of ε-martensite of different types,or simultaneously the microtwins and wafers of ε-martensite,were present in each grain.展开更多
AsSb alloy(0.70−95.81 wt.%As)was prepared by electrodeposition in As(III)and Sb(III)contained electrolytes.The influence of electrolyte composition,hydrochloric acid concentration,and temperature on the composition an...AsSb alloy(0.70−95.81 wt.%As)was prepared by electrodeposition in As(III)and Sb(III)contained electrolytes.The influence of electrolyte composition,hydrochloric acid concentration,and temperature on the composition and structure of AsSb deposits was studied.The electroreduction mechanism of As(III)and Sb(III)in hydrochloric acid solution was revealed via thermodynamic analysis.The results show that the increase of H+concentration promotes the reduction of As(III),while the increase of Cl^(−)concentration significantly inhibits the reduction of Sb(III).As a result,the As content in deposits increases gradually with the increase of hydrochloric acid concentration.Simultaneously,the phase structure of AsSb deposits evolves from crystalline to amorphous.When the As content is 24.55−33.75 wt.%,AsSb mixed crystal is obtained.The electrolysis temperature has little effect on the deposits composition,but the structure of deposits evolves from crystalline to amorphous with decreasing the temperature.展开更多
Broadband phase shifters are mostly proposed and fabricated based on the scheme proposed by Shiffman, which uses a coupled line with far ends connected together and a uniform transmission line to give a differential p...Broadband phase shifters are mostly proposed and fabricated based on the scheme proposed by Shiffman, which uses a coupled line with far ends connected together and a uniform transmission line to give a differential phase shift. Based on the unique dispersion property of the composite right/left-handed (CRLH) metamaterial structure, a new configuration is presented in this paper for fabricating the broadband differential phase shifter, which employs a novel CRLH metamaterial structure as one of the differential phase-shift arms, instead of the conventional coupled line. The new circuit can achieve a phase shift of 90° in an operational bandwidth as broad as one octave and its phase deviations are quite small. An original design of the novel broadband phase shifter is presented, in which the artificial CRLH structure was implemented by microstrip quasi-lumped elements. Both the simulated and measured results of the 90° broadband differential phase shifter are presented.展开更多
Microstructural studies have been made on the Mg-0.54Zr,Mg-5.68Zn and Mg-5.65Zn-0.50Zr alloys in the as-cast and homogenized states.The lenticular plates of {012}twins were found in three alloys.After homogenization,Z...Microstructural studies have been made on the Mg-0.54Zr,Mg-5.68Zn and Mg-5.65Zn-0.50Zr alloys in the as-cast and homogenized states.The lenticular plates of {012}twins were found in three alloys.After homogenization,ZrH_2 phase formed in the Mg-0.54Zr alloy.The Mg_7Zn_3 phase of cubic structure with a=1.417 nm distributes at the grain boundaries of the Mg-5.68Zn alloy in the as-cast state and after homogenization,the Mg_7Zn_3 phase dissolves and the MgZn_2 phase occurs.The as-cast Mg-5.65Zn-0.50Zr al- loy consists of MgZn_3 phase and Zn-Zr compounds.After homogenization,the dispersed acicular MgZn_2 phase may precipitate.展开更多
An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method (TE/QP). The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents ...An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method (TE/QP). The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents and the microstructure of the composites and the particle size of the reinforcement were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results have shown that TiCp/Al composite with 40~70 vol. pct TiC particle reinforcement and high relative density can be directly obtained by TE/QP. TiC is the only reaction product when Al content in Al-Ti-C system is no more than 60 vol. pct, but Al3Ti phase will also form when Al content is more than 60 vol. pct. Increasing Al content prolongs the initial reaction time, reduces the highest reaction temperature and the reaction rate, and decreases the size of TiC particles. In addition, the microstructure of TiCp/Al composite and the structure of interface between TiCp and Al are studied using SEM and transmission electron microscopy (TEM). The results show that the in-situ synthesized TiC particle has fcc cubic structure. The orientation between TiC particles and Al matrix can be described as (220)Al//(022)TiC and [112]Al//[011]TiC. Results of the mechanical property tests reveal that the ultimate strength (σ) and modulus (E) are 687 MPa and 142 GPa respectively when the Al content is 40 vol. pct. On contrary, 6 elongation increases by 3.2% with increasing Al content.展开更多
Nanometer 3Y TZP/20%Al 2O 3 (mass fraction) composite powders prepared by the chemical coprecipitation method were pressureless sintered at 1550 ℃ for 2 h. Effects of calcining temperatures at 800 ℃, 1 000 ℃, and 1...Nanometer 3Y TZP/20%Al 2O 3 (mass fraction) composite powders prepared by the chemical coprecipitation method were pressureless sintered at 1550 ℃ for 2 h. Effects of calcining temperatures at 800 ℃, 1 000 ℃, and 1 200 ℃ on phase structure, relative density, and Vicker′s hardness of the sintered bodies were studied. The results show that 1 000 ℃ was the optimal calcining temperature,and the powder calcined was composed of tetragonal zirconia with the Scherrer crystalline size of 6.3 nm. The relative density was up to 98.5% under pressureless sintering, and the sintered body was t ZrO 2(without m ZrO 2)+α Al 2O 3 with the average size of 0.4 μm.展开更多
Conditions of formation, structure and properties of boride iron layers on carbonaceous steels 3 and 45 at electron beam borating are investigated. New process to make layers of iron borides (Fe2B, FeB) using electr...Conditions of formation, structure and properties of boride iron layers on carbonaceous steels 3 and 45 at electron beam borating are investigated. New process to make layers of iron borides (Fe2B, FeB) using electron beam are reported. The microstructure and microhardness of boride layers are investigated and also are compared to layer properties obtained at solid phase borating. Formed layers were heterogeneous structure combining solid and weak components and resulting in to fragility reduction of boride layer.展开更多
4 mol.% Y203 stabilized ZrO2 (YSZ) doped with various quantifies of Gd203 (G-YSZ) ceramic comings were synthesized by electrophoretic deposition method, and followed by vacuum sintering and isothermally annealing ...4 mol.% Y203 stabilized ZrO2 (YSZ) doped with various quantifies of Gd203 (G-YSZ) ceramic comings were synthesized by electrophoretic deposition method, and followed by vacuum sintering and isothermally annealing at 1000 ℃ for different durations. X-ray diffraction (XRD) was used to investigate their phase composition. Scanning electron microscopy (SEM) was employed to examine their microstructure, while energy dispersive X-ray spectrometer (EDS) was used to assess composition of the composite coatings. The results indicated that YSZ coating was composed of tetragonal and monoclinic phase after vacuum sintefing at 1000 ~C for 2 h under vacuum (〈103 Pa). G-YSZ composite coatings were composed of tetmgonal, monoclinic phase and a small amount of Gd2Zr207 phase after vacuum sintering at 1000 ℃ for 2 h, whereas the content ofmonoclinic phase in G-YSZ composite coatings in- creased with increasing Gd203 concentration. It was found that G-YSZ composite coatings were composed of tetragonal ZrO2 phase, monoclinic ZrO2 phase and cubic phase, whereas Gd2Zr207 phase disappeared, after G-YSZ composite coatings were isothermally annealed at 1000 ℃ in air for 100 h. A detailed description of the results and their discussion was presented in the paper.展开更多
基金Project Supported bythe Talents Development Foundation of Inner Mongolia Autonomous Region (200608)
文摘Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3 alloy has high chemical activity and favorable plateaus pressure. Mg2Ni is in favor of high hydrogen storage capacity and low weight, but it is difficult to be activated. In order to improve the capacity and cycle performances of hydrogen-storage alloy electrodes, Mm0.3Ml0.7Ni3.55Co0.75Mn0.4-Al0.3-x%Mg2Ni(x=0, 5, 10, 30) composite hydrogen storage alloys prepared by two-step re-melting were investigated in this work. The influences of Mg2Ni content on the cycle stabilities were analyzed by electrochemical methods. It was observed by XRD that the main phase of all the alloys is LaNi5 and the crystal lattice parameters of LaNi5 are changed with the increasing of x value, i.e, a-axis and unit cell volume decrease and c-axis decreases nonlinearly. The c-axis of alloy with x=5 is larger than the others. With the increasing of x value, capacity retentions of the composite hydrogen storage alloys rise from 66.21% while x=0 to 82.04% while x=10, but the capacity retention of the composite alloy with 30% Mg2Ni declines because of its decreasing axial ratio. More over, the composite alloy with 5% Mg2Ni shows the best cycle stability and higher discharge capacity, and it is an appropriate candidate for battery materials.
基金Project(NCET-11-0554) supported by the Program for New Century Excellent Talents in University,ChinaProject(2011BAE22B04) supported by the National Key Technology R&D Program,ChinaProject(51271206) supported by the National Natural Science Foundation of China
文摘The microstructure and phase composition of as-cast Mg-9Er-6Y-xZn-0.6Zr (x=1, 2, 3, 4; normal mass fraction in %) alloys were investigated. In low Zn content, aside from the major second phase of Mg24(Er, Y, Zn)5, there are a few lamellar phases that grow parallel with each other from the grain boundaries to the grain interior. With Zn content increasing, the Mg24(Er, Y, Zn)5 phase decreases, but the Mg12Zn(Y, Er) phase and lamellar phases continuously increase. When Zn content reaches 4% (normal mass fraction), the Mg12Zn(Y, Er) phase mainly exists as large bulks, and some a-Mg grains are thoroughly penetrated by the lamellar phases. Moreover, the crystallography structures of the Mgl2Zn(Y, Er) and Mg24(Er, Y, Zn)5 phases are confirmed as 18R-type long-period stacking ordered structure and body-centred cubic structure, respectively.
文摘The general use of aluminium as an indentation standard for the iteration of contact heights for the determination of ISO-14577 hardness and elastic modulus is challenged because of as yet not appreciated phase-changes in the physical force-depth standard curve that seemed to be secured by claims from 1992. The physical and mathematical analyses with closed formulas avoid the still world-wide standardized energy-law violation by not reserving 33.33% (h2 belief) (or 20% h3/2 physical law) of the loading force and thus energy for all not depth producing events but using 100% for the depth formation is a severe violation of the energy law. The not depth producing part of the indentation work cannot be done with zero energy! Both twinning and structural phase-transition onsets and normalized phase-transition energies are now calculated without iterations but with physically correct closed arithmetic equations. These are reported for Berkovich and cubecorner indentations, including their comparison on geometric grounds and an indentation standard without mechanical twinning is proposed. Characteristic data are reported. This is the first detection of the indentation twinning of aluminium at room temperature and the mechanical twinning of fused quartz is also new. Their disqualification as indentation standards is established. Also, the again found higher load phase-transitions disqualify aluminium and fused quartz as ISO-ASTM 14577 (International Standardization Organization and American Society for Testing and Materials) standards for the contact depth “hc” iterations. The incorrect and still world-wide used black-box values for H- and Er-values (the latter are still falsely called “Young’s moduli” even though they are not directional) and all mechanical properties that depend on them. They lack relation to bulk moduli from compression experiments. Experimentally obtained and so published force vs depth parabolas always follow the linear FN = kh3/2 + Fa equation, where Fa is the axis-cut before and after the phase-transition branches (never “h2” as falsely enforced and used for H, Er and giving incorrectly calculated parameters). The regression slopes k are the precise physical hardness values, which for the first time allow for precise calculation of the mechanical qualities by indentation in relation to the geometry of the indenter tip. Exactly 20% of the applied force and thus energy is not available for the indentation depth. Only these scientific k-values must be used for AI-advises at the expense of falsely iterated indentation hardness H-values. Any incorrect H-ISO-ASTM and also the iterated Er-ISO-ASTM modulus values of technical materials in artificial intelligence will be a disaster for the daily safety. The AI must be told that these are unscientific and must therefore be replaced by physical data. Iterated data (3 and 8 free parameters!) cannot be transformed into physical data. One has to start with real experimental loading curves and an absolute ZerodurR standard that must be calibrated with standard force and standard length to create absolute indentation results. .
基金Projects(2019JJ60050,2018JJ3121) supported by the Natural Science Foundation of Hunan Province,ChinaProject(KFBM20170004) supported by the Jiangsu Province Key Laboratory of Materials Surface Science and Technology,China
文摘The microstructures and interface structures of basalt particle reinforced 7A04 Al matrix composites (BP/7A04 Al) were analyzed by using OM, TEM, SEM and EDS, and the mechanical properties of 7A04 Al alloy were compared with those of BP/7A04 Al matrix composites. The results show that the basalt particles are dispersed in the Al matrix and form a strong bonding interface with the Al matrix. SiO2 at the edge of the basalt particles is continuously replaced by Al2O3 formed in the reaction, forming a high-temperature reaction layer with a thickness of several tens of nanometers, and Al2O3 strengthens the bonding interface between basalt particles and Al matrix. The dispersed basalt particles promote the dislocation multiplication, vacancy formation and precipitation of the matrix, and the precipitated phases mainly consist of plate-like η(MgZn2) phase and bright white band-shaped or ellipsoidal T (Al2Mg3Zn3) phase. The bonding interface, high dislocation density and dispersion strengthening phase significantly improve the mechanical properties of the composites. The yield strength and ultimate tensile strength of BP/7A04 Al matrix composites are up to 665 and 699 MPa, which increase by 11.4% and 10.9% respectively compared with 7A04 Al alloy without basalt particles.
文摘It was shown by TEM and X-ray analysis that there are four types of grains of the main Ni3Al phase in the structure of the intermetallic obtained by the self-propagation high temperature method (SHS). Every type of grains has its own domain and dislocation structure. There are mono- and polydomains with and without dislocations. The grains of the main phase of monoand polydomains without dislocations and polydomains with dislocations were formed by diffusion in the solid phase. In these conditions NiAl3 phase is located on the grain boundary of the main phase. The Ni2Al3 phase is located at the triple joints of the main phase.
基金partly supported by the Russian Foundation for basic Researches(No.16-48-700198)the Tomsk State University competitiveness improvement programme
文摘The effect of TiO;,ZrO;and Na;AlF;ultrafine powders on the fine structure and the phase composition of Fe–14Mn–1.2C steel was investigated.The introduction of the ultrafine powders into the melt influenced the grain size,the quantity,and the character of distribution of nonmetallic inclusions in the railroad frogs.The microstructure of castings was improved significantly because of the refinement of the grain structure and an increase of the grain-boundary area.After the modifying mixture was introduced into the melt,either the microtwins of one or two intersecting systems or the precipitations of ε-martensite of different types,or simultaneously the microtwins and wafers of ε-martensite,were present in each grain.
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(No.51374185).
文摘AsSb alloy(0.70−95.81 wt.%As)was prepared by electrodeposition in As(III)and Sb(III)contained electrolytes.The influence of electrolyte composition,hydrochloric acid concentration,and temperature on the composition and structure of AsSb deposits was studied.The electroreduction mechanism of As(III)and Sb(III)in hydrochloric acid solution was revealed via thermodynamic analysis.The results show that the increase of H+concentration promotes the reduction of As(III),while the increase of Cl^(−)concentration significantly inhibits the reduction of Sb(III).As a result,the As content in deposits increases gradually with the increase of hydrochloric acid concentration.Simultaneously,the phase structure of AsSb deposits evolves from crystalline to amorphous.When the As content is 24.55−33.75 wt.%,AsSb mixed crystal is obtained.The electrolysis temperature has little effect on the deposits composition,but the structure of deposits evolves from crystalline to amorphous with decreasing the temperature.
基金Project supported by the National Basic Research Program (973) of China (No. 2004CB719802)the National Natural Science Founda-tion of China (No. 60378037)the Science and Technology Department of Zhejiang Province, China (No. 2005C31004)
文摘Broadband phase shifters are mostly proposed and fabricated based on the scheme proposed by Shiffman, which uses a coupled line with far ends connected together and a uniform transmission line to give a differential phase shift. Based on the unique dispersion property of the composite right/left-handed (CRLH) metamaterial structure, a new configuration is presented in this paper for fabricating the broadband differential phase shifter, which employs a novel CRLH metamaterial structure as one of the differential phase-shift arms, instead of the conventional coupled line. The new circuit can achieve a phase shift of 90° in an operational bandwidth as broad as one octave and its phase deviations are quite small. An original design of the novel broadband phase shifter is presented, in which the artificial CRLH structure was implemented by microstrip quasi-lumped elements. Both the simulated and measured results of the 90° broadband differential phase shifter are presented.
文摘Microstructural studies have been made on the Mg-0.54Zr,Mg-5.68Zn and Mg-5.65Zn-0.50Zr alloys in the as-cast and homogenized states.The lenticular plates of {012}twins were found in three alloys.After homogenization,ZrH_2 phase formed in the Mg-0.54Zr alloy.The Mg_7Zn_3 phase of cubic structure with a=1.417 nm distributes at the grain boundaries of the Mg-5.68Zn alloy in the as-cast state and after homogenization,the Mg_7Zn_3 phase dissolves and the MgZn_2 phase occurs.The as-cast Mg-5.65Zn-0.50Zr al- loy consists of MgZn_3 phase and Zn-Zr compounds.After homogenization,the dispersed acicular MgZn_2 phase may precipitate.
文摘An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method (TE/QP). The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents and the microstructure of the composites and the particle size of the reinforcement were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results have shown that TiCp/Al composite with 40~70 vol. pct TiC particle reinforcement and high relative density can be directly obtained by TE/QP. TiC is the only reaction product when Al content in Al-Ti-C system is no more than 60 vol. pct, but Al3Ti phase will also form when Al content is more than 60 vol. pct. Increasing Al content prolongs the initial reaction time, reduces the highest reaction temperature and the reaction rate, and decreases the size of TiC particles. In addition, the microstructure of TiCp/Al composite and the structure of interface between TiCp and Al are studied using SEM and transmission electron microscopy (TEM). The results show that the in-situ synthesized TiC particle has fcc cubic structure. The orientation between TiC particles and Al matrix can be described as (220)Al//(022)TiC and [112]Al//[011]TiC. Results of the mechanical property tests reveal that the ultimate strength (σ) and modulus (E) are 687 MPa and 142 GPa respectively when the Al content is 40 vol. pct. On contrary, 6 elongation increases by 3.2% with increasing Al content.
文摘Nanometer 3Y TZP/20%Al 2O 3 (mass fraction) composite powders prepared by the chemical coprecipitation method were pressureless sintered at 1550 ℃ for 2 h. Effects of calcining temperatures at 800 ℃, 1 000 ℃, and 1 200 ℃ on phase structure, relative density, and Vicker′s hardness of the sintered bodies were studied. The results show that 1 000 ℃ was the optimal calcining temperature,and the powder calcined was composed of tetragonal zirconia with the Scherrer crystalline size of 6.3 nm. The relative density was up to 98.5% under pressureless sintering, and the sintered body was t ZrO 2(without m ZrO 2)+α Al 2O 3 with the average size of 0.4 μm.
文摘Conditions of formation, structure and properties of boride iron layers on carbonaceous steels 3 and 45 at electron beam borating are investigated. New process to make layers of iron borides (Fe2B, FeB) using electron beam are reported. The microstructure and microhardness of boride layers are investigated and also are compared to layer properties obtained at solid phase borating. Formed layers were heterogeneous structure combining solid and weak components and resulting in to fragility reduction of boride layer.
基金Project supported by Shanghai Municipal Developing Foundation of Science and Technology (0852nm01400)National Training Programs of Innovation for Undergraduates (201210856022)Science and Technology Key Fund Project of Shanghai University of Engi-neering Science (2011XZ07) for financial support
文摘4 mol.% Y203 stabilized ZrO2 (YSZ) doped with various quantifies of Gd203 (G-YSZ) ceramic comings were synthesized by electrophoretic deposition method, and followed by vacuum sintering and isothermally annealing at 1000 ℃ for different durations. X-ray diffraction (XRD) was used to investigate their phase composition. Scanning electron microscopy (SEM) was employed to examine their microstructure, while energy dispersive X-ray spectrometer (EDS) was used to assess composition of the composite coatings. The results indicated that YSZ coating was composed of tetragonal and monoclinic phase after vacuum sintefing at 1000 ~C for 2 h under vacuum (〈103 Pa). G-YSZ composite coatings were composed of tetmgonal, monoclinic phase and a small amount of Gd2Zr207 phase after vacuum sintering at 1000 ℃ for 2 h, whereas the content ofmonoclinic phase in G-YSZ composite coatings in- creased with increasing Gd203 concentration. It was found that G-YSZ composite coatings were composed of tetragonal ZrO2 phase, monoclinic ZrO2 phase and cubic phase, whereas Gd2Zr207 phase disappeared, after G-YSZ composite coatings were isothermally annealed at 1000 ℃ in air for 100 h. A detailed description of the results and their discussion was presented in the paper.