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Wang X.,Western Superconducting Technologies Co. | Wang X.,Northwestern Polytechnical University
Jinshu Rechuli/Heat Treatment of Metals | Year: 2013

Effects of annealing and deforming temperatures on the transformation and deformation of Ti-50.1Ni shape memory alloy have been investigated by means of thermal gravity, X-ray diffraction and tensile test. Oxidation become serious above 600°C in the process of heating for Ti-50.1Ni, therefore, annealing temperature should be below 600°C. Since austenitic transformation start temperatures (As) is above room temperature, the phase at the room temperature is martensitic phase, the Ti-50.1Ni alloy shows shape memory effect (SME). The SME property can be obtained at room temperature for the Ti-50.1Ni alloy annealed at 350-600°C. Source

Chen Y.,Northwestern Polytechnical University | Li J.,Northwestern Polytechnical University | Tang B.,Northwestern Polytechnical University | Kou H.,Northwestern Polytechnical University | And 3 more authors.
Materials Letters | Year: 2013

Grain boundary character distribution and texture evolution of Ti-45Nb wires were investigated during the cold-drawn process. The results revealed that the fiber microstructure formed along drawing direction after cold-drawn process. The <110> fiber texture formed and the intensity enhanced by increasing the strain from 90% to 98% during the cold-drawn process. A large amount of high angle grain boundaries (HAGB) occurred at a large strain state of 90%, which was resulted from the rotation of the initial β grains. By increasing the strain to 98%, the fraction of low angle grain boundaries (LAGB) increased remarkably by the formation of the subdivided grains. © 2013 Elsevier B.V. All rights reserved. Source

Li C.S.,Northwest Institute for Nonferrous Metal Research | Yang F.,Northwest Institute for Nonferrous Metal Research | Yan G.,Western Superconducting Technologies Co. | Xiong X.M.,Northwest Institute for Nonferrous Metal Research | And 5 more authors.
Journal of Alloys and Compounds | Year: 2014

Superhard materials AlMgB14-xTiB2 disks were synthesized by a two-step heat-treatment method. In the first step, AlMg 6B14-xTiB2 disks were fabricated by uniformly mixed Mg, B, Al powders and different contents Ti powder, and then AlMg 6B14-xTiB2 disks were heated at 850 C for 2 h in closed argon atmosphere. In the second step, AlMg6B 14-xTiB2 disks were sintered at 1050 C for half an hour in vacuum, then target AlMgB14-xTiB2 disks were obtained. The phase, microstructure and superconductivity were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and superconducting quantum interference device (SQUID). The nano-scale TiB2 particles as the second phase induced by Ti doping are uniformly distributed in the sample matrix. The results reveal that the stepwise synthesis method can produce practical AlMgB14-TiB2 materials. © 2013 Elsevier B.V. All rights reserved. Source

Han F.,Northwestern Polytechnical University | Tang B.,Northwestern Polytechnical University | Kou H.,Northwestern Polytechnical University | Cheng L.,Northwestern Polytechnical University | And 3 more authors.
Journal of Materials Science | Year: 2014

This study presents a 2D cellular automata simulation of static recrystallization (SRX) arising from the subgrain growth in single-phase material following cold deformation by coupling with a crystal plasticity finite element (CPFE) method. The spatial distribution of the stored deformation energy was obtained by CPFE simulation, based on which the initial deformed microstructure consisting of nonuniformly distributed subgrains was predicted. To simulate grain/subgrain growth during annealing, a curvature-driven mechanism was used, in which the grain/subgrain boundary energy and mobility were misorientation-dependent. On the SRX nucleation, a physically based model using critical subgrain size as criterion was adopted, which could provide better insight into the recrystallization nucleation mechanism involving grain boundary bulging. Simulations under different pre-deformation conditions were performed, and the influence of strain rate and strain on the SRX microstructure evolution and the transformation kinetics were investigated. Results show that deformation at higher strain rate can accelerate the SRX kinetics, and the SRX behavior depends more on the deformation state of individual grain than the nominal strain due to the relatively small computational domain. © 2014 Springer Science+Business Media New York. Source

Wang Q.X.,Xian University of Science and Technology | Wang Q.X.,Western Superconducting Technologies Co. | Liang S.H.,Xian University of Science and Technology
Vacuum | Year: 2011

An W-10 wt.%Ti alloy target was prepared by the W-Ti ball-milled powders, and W-Ti thin lms were deposited by dc magnetron sputtering on Si substrates. Then Cu/W-Ti/Si structures were prepared after Cu films were deposited on the W-Ti/Si structures. The results show that W-Ti alloy has a single phase structure with fine grain size. The structures of W-Ti thin films evolved from an amorphous film to a dual phase structure with bcc W and hcp Ti, followed by W-Ti solid solution with increasing sputtering powers. W-Ti thin lms can effectively block against Cu diffusion and maintain good adhesion strength with Cu lms at 600 °C. The failure mechanism of the crystal W-Ti films is related to the grain boundary which provides fast diffusion paths for Cu and Si atoms, while the amorphous W-Ti diffusion barrier layer is directly related to the thermal stress and interface reaction. © 2011 Elsevier Ltd. All rights reserved. Source

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