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        Wear Behavior of P/M High Nb Containing γ-TiAl Alloy in Different Environments

        Jingwen Qiu,Zhengfan Fu,Bin Liu,Yong Liu,Jianhui Yan,Di Pan,Weidong Zhang 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.6

        The wear behavior of Ti–45Al–7Nb–0.3W (at%) alloy prepared by powder metallurgy (P/M) has been investigated using pinon-disk wear tests at the room temperature. The dry sliding wear tests were performed against on a zirconia disk in differentenvironments, viz, argon, hydrogen in nitrogen mixture, air and oxygen. The worn surfaces of Ti–45Al–7Nb–0.3W pins andwear debris were examined by scanning electron microscope, X-ray diffractometer and X-ray photoelectron spectroscopy. It was found that the high Nb containing Ti–45Al–7Nb–0.3W alloy didn’t exhibit better wear resistance in the presence ofoxygen than commercial γ-TiAl (Ti–47Al–2Nb–2Cr–0.2W) alloy. The oxidation on the worn surface and spalling of oxidescaused by the mechanical force during sliding were the main reason for the high wear losses in the air and oxygen. Thezirconia disk underwent a phase transformation caused by the high contact temperature and stress during the sliding tests. The abrasive particles produced in the wear tests largely consisted of the zirconia particles in different environments, exceptin the pure oxygen. The hard zirconia debris was embedded into the friction layer on the worn surfaces of TiAl pins, whichprovided protection against wear to some extent. The main wear mechanisms of Ti–45Al–7Nb–0.3W alloy were abrasivewear of two-body and three-body, some delamination and plastic deformation.

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        Single Low-Light Ghost-Free Image Enhancement via Deep Retinex Model

        ( Yan Liu ),( Bingxue Lv ),( Jingwen Wang ),( Wei Huang ),( Tiantian Qiu ),( Yunzhong Chen ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.5

        Low-light image enhancement is a key technique to overcome the quality degradation of photos taken under scotopic vision illumination conditions. The degradation includes low brightness, low contrast, and outstanding noise, which would seriously affect the vision of the human eye recognition ability and subsequent image processing. In this paper, we propose an approach based on deep learning and Retinex theory to enhance the low-light image, which includes image decomposition, illumination prediction, image reconstruction, and image optimization. The first three parts can reconstruct the enhanced image that suffers from low-resolution. To reduce the noise of the enhanced image and improve the image quality, a super-resolution algorithm based on the Laplacian pyramid network is introduced to optimize the image. The Laplacian pyramid network can improve the resolution of the enhanced image through multiple feature extraction and deconvolution operations. Furthermore, a combination loss function is explored in the network training stage to improve the efficiency of the algorithm. Extensive experiments and comprehensive evaluations demonstrate the strength of the proposed method, the result is closer to the real-world scene in lightness, color, and details. Besides, experiments also demonstrate that the proposed method with the single low-light image can achieve the same effect as multi-exposure image fusion algorithm and no ghost is introduced.

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        Microstructure and Mechanical Properties of Cold Drawn Ti–Nb–Ta–Zr–O Wires for Orthodontic Applications

        Wei‑dong Zhang,Junye Ren,Bin Liu,Yong Liu,Zhenggang Wu,Jingwen Qiu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.7

        Ti–36Nb–2Ta–3Zr–0.35O (TNTZO) alloy is an excellent candidate for biomedical applications. In this study, a new methodcombining cold-swaging and cold-drawing was used to fabricate the TNTZO alloy wires with 0.3 mm diameter for orthodonticapplications. The microstructure and mechanical properties of cold-drawn and annealed TNTZO wires (referred toas TNTZO0.3and TNTZO0.3(HT), respectively) were investigated. The results show that the microstructure of cold drawnTNTZO0.3consists of main-sized elongated grains with 70 nm width. After annealing at 700 °C for 5 min, the microstructureof TNTZO0.3(HT) wires becomes equiaxial with a grain size of ~ 5 μm. The cold drawn TNTZO0.3wires exhibit improvedmechanical properties, higher tensile strength (about 1000 MPa) and similar elastic modulus (69 GPa), compared to annealedTNTZO0.3(HT) wires. Besides, TNTZO0.3has higher creep resistance and lower stress exponent (around 2), compared to Tiwires and TC4 wires with the same diameter. These results prove that TNTZO0.3wires have most of the ideal characteristicsof orthodontic wires.

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