The powders of pure Al, Fe, and Zr for preparing Al78Fe20Zr2 were subject to a high-energy planetary ball milling.The microstructure evolution of the mixtures at the different intervals of milling was characterized by...The powders of pure Al, Fe, and Zr for preparing Al78Fe20Zr2 were subject to a high-energy planetary ball milling.The microstructure evolution of the mixtures at the different intervals of milling was characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and differential scanning calorimetry（DSC）.It was found that a nearly complete amorphization could be achieved in the mixtures after ball milling for 23 h.Further ball milling led to the crystallization of the amorphous powders.A long time ball milling, e.g., 160 h, led to a complete crystallization of the amorphous powders and the formation of Al3Zr and Al13Fe4.The crystallization products caused by ball milling are almost the same as that produced by isothermal annealing of the amorphous powders in vacuum at 800 K for 1 h.展开更多
Starting from elemental powders, complete MoSi2 powder forms abruptly between 3.5and 4 h during mechanical alloying (MA) of the Mo-66 at.% Si powders. Continuous milling of this MoSi2 Phase leads to a nanocrystalline ...Starting from elemental powders, complete MoSi2 powder forms abruptly between 3.5and 4 h during mechanical alloying (MA) of the Mo-66 at.% Si powders. Continuous milling of this MoSi2 Phase leads to a nanocrystalline powder and amorphizationtransformation takes place after 100 h milling. Howeven MA of the Mo-37.5 at.%Si powders does not result in the formation of the Mo5Si3 crystalline phase, but the formation of a Mo(Si) supersaturated solid solution (SSS) and a completely amorphots phase after 5 h and 70 h milling, respectively. The free energy of the Mo-Sisystem has been calculated and it has been found that there is no driving force for the amorphization reaction under normal conditions. The amorphization by MA of the Mo-Si system is attributed to a solid-state amorphization reaction in which defects and a very fine grain size induced during milling process may raise the free energy of the crystalline intermetallic phase (for MoSi2) or the Mo(Si) supersaturated solid solution (for Mo5Si3) above that of the amorphous phase.展开更多
A titanium alloy containing continuous oxygen gradient was prepared by powder metallurgy(P/M) and the composition–property relationship was studied on a single sample. The alloy was sintered with layered powder of di...A titanium alloy containing continuous oxygen gradient was prepared by powder metallurgy(P/M) and the composition–property relationship was studied on a single sample. The alloy was sintered with layered powder of different oxygen contents via vacuum sintering and spark plasma sintering(SPS), respectively. After subsequent heat treatments, high-throughput characterizations of the microstructures and mechanical properties by localized measurements were conducted. The Ti-7% Mo(molar fraction) alloy with an oxygen content ranging from 1.3×10^(-3) to 6.2×10^(-5)(mass fraction) was obtained, and the effects of oxygen on the microstructural evolution and mechanical properties were studied. The results show that SPS is an effective way for fabricating fully dense Ti alloy with a compositional gradient. The average width of α′ phase coarsens with the increase of the content of oxygen. The content of α″ martensitic phase also increases with the content of oxygen. At oxygen contents of 3×10^(-3) and 4×10^(-3)(mass fraction), the Ti alloys present the lowest microhardness and the lowest elastic modulus, respectively. The results also indicate that the martensitic phases actually decrease the hardness of Ti-7Mo alloy, and oxygen effectively hardens the alloy by solid solution strengthening. Therefore, the high-throughput characterization on a microstructure with a gradient content of oxygen is an effective method for rapidly evaluating the composition–property relationship of titanium alloys.展开更多
The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying...The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying the composition, i.e. fully or partially replacing rare earth （RE） and transition metal （TM） elements based on similar atomic radii and coordination number. X-ray diffraction and high resolution transmission electron microscopy study revealed that the amorphization process occurred through formation of various intermetallic phases and nanocrystalline FCC Al. Fully amorphous phase was obtained for the alloys not containing lanthanum, whereas the other alloys containing La showed partial amorphization with reappearance of intermetallic phases attributed to mechanical crystallization. Differential scanning calorimetry study confirmed better thermal stability with wider transformation temperature for the alloys without La.展开更多
To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post milling.Annealing above the crystallization temperature（T...To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post milling.Annealing above the crystallization temperature（Tx） not only induced nanoscale intermetallics to precipitate in the amorphous powder,but also increased Cu atomic percentage within the residual amorphous phase.Post milling induced the amorphization of the nanocrystal intermetallics and the formation of Cu9Al4 from the residual amorphous phase.Thus,a mixed structure consisting of amorphous phase and Cu9Al4 was obtained in the powder after annealing and post milling（the APMed powder）.The phase constituent in the APMed powder did not change during the post annealing,which exhibited significantly improved thermal stability in comparison with the as-milled amorphous powder.展开更多
采用分段机械球磨-放电等离子烧结法,进行了节能变压器用新型非晶合金Fe77Si9B13Ce0.5Nb0.2Cr0.3,并进行了XRD、SEM分析和软磁性能、力学性能和耐腐蚀性能的测试。结果表明,与现有非晶合金Fe78Si9B13相比,该新型非晶合金的软磁性能、力...采用分段机械球磨-放电等离子烧结法,进行了节能变压器用新型非晶合金Fe77Si9B13Ce0.5Nb0.2Cr0.3,并进行了XRD、SEM分析和软磁性能、力学性能和耐腐蚀性能的测试。结果表明,与现有非晶合金Fe78Si9B13相比,该新型非晶合金的软磁性能、力学性能和耐腐蚀性能均得到明显改善,其中初始磁导率和饱和磁感应强度分别增加了70%、32%,20℃时试样的抗拉强度和伸长率分别增加36%、4.4%,腐蚀电位正移268 m V。展开更多
基金financial support of the National Natural Science Foundation of China (No. 50371072)the Hunan Provincial Natural Science Foundation (No. 09JJ3086)
文摘The powders of pure Al, Fe, and Zr for preparing Al78Fe20Zr2 were subject to a high-energy planetary ball milling.The microstructure evolution of the mixtures at the different intervals of milling was characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM） and differential scanning calorimetry（DSC）.It was found that a nearly complete amorphization could be achieved in the mixtures after ball milling for 23 h.Further ball milling led to the crystallization of the amorphous powders.A long time ball milling, e.g., 160 h, led to a complete crystallization of the amorphous powders and the formation of Al3Zr and Al13Fe4.The crystallization products caused by ball milling are almost the same as that produced by isothermal annealing of the amorphous powders in vacuum at 800 K for 1 h.
文摘Starting from elemental powders, complete MoSi2 powder forms abruptly between 3.5and 4 h during mechanical alloying (MA) of the Mo-66 at.% Si powders. Continuous milling of this MoSi2 Phase leads to a nanocrystalline powder and amorphizationtransformation takes place after 100 h milling. Howeven MA of the Mo-37.5 at.%Si powders does not result in the formation of the Mo5Si3 crystalline phase, but the formation of a Mo(Si) supersaturated solid solution (SSS) and a completely amorphots phase after 5 h and 70 h milling, respectively. The free energy of the Mo-Sisystem has been calculated and it has been found that there is no driving force for the amorphization reaction under normal conditions. The amorphization by MA of the Mo-Si system is attributed to a solid-state amorphization reaction in which defects and a very fine grain size induced during milling process may raise the free energy of the crystalline intermetallic phase (for MoSi2) or the Mo(Si) supersaturated solid solution (for Mo5Si3) above that of the amorphous phase.
基金Project(2014CB6644002)supported by the National Basic Research Program of ChinaProject(2015CX004)supported by the Innovation-driven Plan in Central South University,China+2 种基金Project(51301203)supported by the National Natural Science Foundation of ChinaProject(2014M551827)supported by the National Science Foundation for Post-doctoral Scientists of ChinaProject(2014GK3078)supported by the Science and Technology Planning of Hunan Province,China
文摘A titanium alloy containing continuous oxygen gradient was prepared by powder metallurgy(P/M) and the composition–property relationship was studied on a single sample. The alloy was sintered with layered powder of different oxygen contents via vacuum sintering and spark plasma sintering(SPS), respectively. After subsequent heat treatments, high-throughput characterizations of the microstructures and mechanical properties by localized measurements were conducted. The Ti-7% Mo(molar fraction) alloy with an oxygen content ranging from 1.3×10^(-3) to 6.2×10^(-5)(mass fraction) was obtained, and the effects of oxygen on the microstructural evolution and mechanical properties were studied. The results show that SPS is an effective way for fabricating fully dense Ti alloy with a compositional gradient. The average width of α′ phase coarsens with the increase of the content of oxygen. The content of α″ martensitic phase also increases with the content of oxygen. At oxygen contents of 3×10^(-3) and 4×10^(-3)(mass fraction), the Ti alloys present the lowest microhardness and the lowest elastic modulus, respectively. The results also indicate that the martensitic phases actually decrease the hardness of Ti-7Mo alloy, and oxygen effectively hardens the alloy by solid solution strengthening. Therefore, the high-throughput characterization on a microstructure with a gradient content of oxygen is an effective method for rapidly evaluating the composition–property relationship of titanium alloys.
基金financial support obtained from the Science and Engineering Research Board,Department of Science & Technology,Government of India(SB/S3/ME/0044/2013)Sponsored Research and Industrial Consultancy,Indian Institute of Technology Kharagpur,India(GAF)
文摘The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys （Al86Ni8Y6, Al86GNi6Y6Co2, Al86NigLa6 and Al86Ni8Y45La15） synthesized via mechanical alloying by varying the composition, i.e. fully or partially replacing rare earth （RE） and transition metal （TM） elements based on similar atomic radii and coordination number. X-ray diffraction and high resolution transmission electron microscopy study revealed that the amorphization process occurred through formation of various intermetallic phases and nanocrystalline FCC Al. Fully amorphous phase was obtained for the alloys not containing lanthanum, whereas the other alloys containing La showed partial amorphization with reappearance of intermetallic phases attributed to mechanical crystallization. Differential scanning calorimetry study confirmed better thermal stability with wider transformation temperature for the alloys without La.
基金supported by the National Natural Science Foundation of China(Grant Nos.51271036 and 51471035)
文摘To improve thermal stability of the Al65Cu16.5Ti18.5 amorphous powder,structural modification of the amorphous powder was performed through annealing and post milling.Annealing above the crystallization temperature（Tx） not only induced nanoscale intermetallics to precipitate in the amorphous powder,but also increased Cu atomic percentage within the residual amorphous phase.Post milling induced the amorphization of the nanocrystal intermetallics and the formation of Cu9Al4 from the residual amorphous phase.Thus,a mixed structure consisting of amorphous phase and Cu9Al4 was obtained in the powder after annealing and post milling（the APMed powder）.The phase constituent in the APMed powder did not change during the post annealing,which exhibited significantly improved thermal stability in comparison with the as-milled amorphous powder.
文摘采用分段机械球磨-放电等离子烧结法,进行了节能变压器用新型非晶合金Fe77Si9B13Ce0.5Nb0.2Cr0.3,并进行了XRD、SEM分析和软磁性能、力学性能和耐腐蚀性能的测试。结果表明,与现有非晶合金Fe78Si9B13相比,该新型非晶合金的软磁性能、力学性能和耐腐蚀性能均得到明显改善,其中初始磁导率和饱和磁感应强度分别增加了70%、32%,20℃时试样的抗拉强度和伸长率分别增加36%、4.4%,腐蚀电位正移268 m V。
