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Zhang Y.,Tongji University | Zhang Y.,Shanghai Key Laboratory of D and A for Metal Functional Materials | Yan B.,Tongji University | Yan B.,Shanghai Key Laboratory of D and A for Metal Functional Materials | And 5 more authors.
Journal of Alloys and Compounds | Year: 2013

The nanocrystallization kinetics of the (Fe0.8Ni 0.15M0.05)78Si8B14 (M = Nb, Ta, W) amorphous alloy was investigated by differential scanning calorimetry (DSC). Kissinger method, Ozawa method and the expended Friedman method were used to calculate and compare the kinetic parameters of the crystallization processes. The nanocrystallization mechanism for the non-isothermal primary crystallization of the amorphous alloys were discussed using Avrami exponent n. Transmission electron microscopy (TEM) studies verified the influence of nanocrystallization mechanism on the microstructure. © 2013 Published by Elsevier B.V. Source


Yang Y.,Tongji University | Yang Y.,Shanghai Key Laboratory of D and A for Metal Functional Materials | Yan B.,Tongji University | Yan B.,Shanghai Key Laboratory of D and A for Metal Functional Materials | And 4 more authors.
Corrosion Science | Year: 2011

In the simulated heat affected zone of 2205 duplex stainless steels, effects of large welding heat inputs on the microstructure and corrosion behaviour were investigated. Reformed austenite content increased with the coarsening of grain boundary austenite (GBA) and the growth of intragranular austenite (IGA) and Widmanstatten austenite (WA), thus improving the low temperature toughness and affecting corrosion state. Reduction of chromium nitrides contributed to better resistance to pitting corrosion. Moreover, the pitting corrosion and intergranular corrosion were improved resulting from the formation of more GBA and WA. The specimen with a Δt8/5 of 100s presents better comprehensive performance. © 2011 Elsevier Ltd. Source


Yang Y.H.,Tongji University | Yang Y.H.,Shanghai Key Laboratory of D and A for Metal Functional Materials | Yan B.,Tongji University | Yan B.,Shanghai Key Laboratory of D and A for Metal Functional Materials | And 4 more authors.
Journal of Alloys and Compounds | Year: 2011

In 25% Cr duplex stainless steels, the effect of prior-solution treatment temperature (STT) on the microstructure and corrosion behavior with ageing at 750 °C and 850 °C was investigated. The results revealed that the precipitation rate of σ-phase was fast in the early stage of ageing for 80 min, and then got slower with ageing time up to 330 min. The σ-phase formation was effectively suppressed by raising STT from 1060 °C to 1230 °C especially for ageing at 750 °C. Consequently, the corrosion rate of specimen was dependent on the amount of σ-phase precipitation, and was lowered due to higher STT, and more σ-phase precipitation can lead to the transition from metastable to stable pitting with ageing at 750 °C up to 330 min. Pitting occurred easily around coarse σ precipitates and caused selective dissolution in ferrite. The longer ageing time increased intergranular corrosion (IGC) susceptibility, whereas higher STT contributed to better resistance to IGC. © 2011 Elsevier B.V. All rights reserved. Source


Lei H.,Tongji University | Lei H.,Shanghai Key Laboratory of D and A for Metal Functional Materials | Zhang Y.,Tongji University | Zhang Y.,Shanghai Key Laboratory of D and A for Metal Functional Materials | And 6 more authors.
Materialwissenschaft und Werkstofftechnik | Year: 2014

Al-8Fe-4Ce alloy is currently manufactured by consolidating the atomized powders. With the aim to reduce the cost, spray forming process was applied in manufacturing with misch metal as raw materials. Spray forming (SF) as well as casting were employed to prepare Al-8Fe-4RE alloy, followed by hot-press to compact the samples. The mechanical properties of SFed and cast Al-8Fe-4RE alloys are characterized at a temperature of 350 °C. The results show that the Al3Fe phases contained in SF alloy is comparatively refined, forming needle-shaped phases embedded in the Al matrix, and the SF alloy also showed lower degree of preferred orientation in (111) plane. Although both factors might explain the superior performance of the SF sample, the fracture appearance after tensile test at 350 °C shows that the contribution from crystallographic feature might be predominant. Spray forming is proved to be a very promising technique for manufacture of Al-Fe-Ce alloys of high strength at an elevated temperature. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Qi H.,Tongji University | Qi H.,Shanghai Key Laboratory of D and A for Metal Functional Materials | Yan B.,Tongji University | Yan B.,Shanghai Key Laboratory of D and A for Metal Functional Materials | And 6 more authors.
Current Nanoscience | Year: 2011

Magnetite (Fe3O4) nanoparticles in the interval of 9~12nm have been synthesized by an non-alkoxide sol-gel method. Through this simple technique, sol-gel materials were prepared from ethanolic solutions of metal chlorides without the need for alkoxides, polymeric gel agents, or elaborate reaction schemes. The gel formation has been studied, and the research shows that gel formation appears to be driven primarily by the formation of an Fe(III)-based network which incorporates Fe(II) into its nanoscale solid domains. The research of the annealing process indicates that magnetite (Fe3O4) nanoparticles can be obtained by annealing only under vacuum, but not in air. Future, Fe3O4 can be oxidized to Fe3O4, as evidenced by XRD, and VSM. The phase structures, morphologies, and particle sizes of Fe3O4 nanoparticles were characterized by thermogravimetric-differential thermal analysis (TG-DTA), X-ray Diffraction (XRD) and Transmis-sion Electron Microscopy (TEM). The results indicate that magnetite (Fe3O4) nanoparticles are homogeneous and have near-spherical shape with a narrow distribution in particle size. Finally, an investigation of the possible mechanism of Fe3O4 nanoparticles formation was performed. Both TG-DTA and X-ray Diffraction (XRD) studies suggest that the reaction of the decomposition of the precursor under vacuum conditions leads to Fe3O4 nanoparticles, while the precursors in air atmosphere is directly oxidized to gamma iron oxide. In addition, this approach may suggest a general route to produce complex multicomponent metal oxide in which the nanoscale oxide is stabilized and spatially distributed. © 2011 Bentham Science Publishers Ltd. Source

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