Papers by Author: Qing Feng Wang

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Authors: Jian Ruan, Qing Feng Wang, L.B. Zhang, Ju Long Yuan, Q.H. Yang
Authors: Hang Su, Xi Qing Zhao, Tao Pan, Xiao Rong Lei, Qing Feng Wang
Abstract: Microstructure and mechanical properties in QT-Treated 9Ni steel were investigated. The detail microstructures were observed by optical microscope (OM) and transmission electron microscope (TEM). The volume fraction of austenite was estimated by XRD. Tensile test at room temperature and Charpy-V-Notch (CVN) impact test at -196°C were carried out. The results showed that the microstructure of QT-treated 9%Ni steel was composed of tempered martensite and reversed austenite. The brittle cementite was absorbed gradually by the increasing reversed austenite as the tempering temperature increased. The optimum tempering temperature range was 560°C~580°C. The reversed austenite could improve the cryogenic toughness of 9Ni steel through the combination of the scavenging effect and the TRIP effect.
Authors: Qing Feng Wang, Cheng Jia Shang, Ya Nan Wang, Wayne Chen
Abstract: In this paper, the very rapid thermal cycles imposed on an ultrafine grain steel plate were successfully simulated using a Gleeble™ simulator. The simulated heat affected zone was obtained suitable for Vickers hardness and impact toughness examination of laser weld that originally bear a narrow zone with high hardness gradient. Effect of preheat treatment on the mechanical behavior of laser HAZ was estimated. It was indicated that the simulated HAZ was composed of fine martensitic ferrite laths with average width in 65nm and 175nm in the case of preheat at 200°C and not, respectively. The laths were cramped by retained austenite film within the prior austenite grain with average size of 9.5 and 6.5μm, much less than that of base metal. The impact toughness of HAZ was improved by laser thermal cycle comparing to that of base metal, and there is no obvious brittle-ductile transition under temperatures from -80°C to 20°C. Preheat treatment of steel plate prior to laser welding resulted in an effective reduction of the maximum hardness and alleviation of the hardness gradient in the weld.
Authors: Qing Feng Wang, Peng Cheng Zhang, Xiao Hong Wang, Da Peng Ren, Ding Mu Lang, Yan Zhi Zhang
Abstract: Microstructure of nickel deposit ,which was prepared with pulse-plating technology on depleted uranium surface, has been studied by X-ray diffractometry(XRD),Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The results indicate that the crystallographic structure of the deposit is face centered cubic; the deposit has a highly preferred orientation of (200), the relative orientation density of (200) is 3.44; the average grain size is about 45.5nm. The deposit is fine and has multi-crystal nature as well as crystallographic defects as dislocation, stacking and twin. It’s feasible to prepare nanocrystalline nickel deposit on depleted uranium surface with pulse plating technology.
Authors: Duan Jun Wang, Yu Hui Wang, Li Gang Liu, Wen Jun Liu, Xi Qing Zhao, Qing Feng Wang
Abstract: The SHCCT (simulated heat affected zone continuous cooling transformation) of 9Ni cryogenic steel were investigated. The microstructures observed in simulated heat affected zone (HAZ) continuous cooled specimens are composed of bainite (B) and martensite (M) depending on the cooling rates. The dimension of prior austensite grain, M-A constituent content, M-A dimension, M-A area density increase with increased the time of t8/5.
Authors: Qing Feng Wang, Cheng Jia Shang, R.D. Fu, Ya Nan Wang, Wayne Chen
Abstract: Two major challenges in relation to laser welding are abrupt change in metallurgical aspects and actual assessment of the mechanical properties due partly to very narrow heat affected zone (HAZ) and partly to high mechanical properties gradient. The rapid thermal cycle of laser welding imposed on the HAZ was physically simulated using a Gleeble™ dynamic simulator equipped with a special isothermal quenching device (ISO-Q™), and a relatively large volume of HAZ with a homogeneous microstructure was obtained. The thermal cycles were determined from actual laser welding followed by laser tempering. Estimations of microstructure and mechanical properties of the simulated HAZs of an ultrafine grain steel imposed by laser welding with or without post-weld laser tempering were performed. The results indicate that the simulated HAZs, depending on the thermal history, are composed of lathy martensite with different pocket size and dislocation density. The impact toughness of as-welded HAZ is improved in contrast to the base material, but is further degraded by a following laser tempering, which, however, alleviates the abrupt change in hardness of as-welded HAZ.
Authors: Bin Guo, Jin Qiao Xu, Lei Cui, Qing Feng Wang
Abstract: This paper provided a detailed description of X90 pipeline steel developed in Wuhan Iron and Steel Corporation (WISCO), including its metallurgical design, manufacturing process, structural characteristics and mechanical properties. Some key issues such as the cooling rate and rolling parameters were addressed for the development of X90 pipeline steel. The experimental results showed that the manufacturing process of controlled rolling (for austenite refining) + relaxation (for ferrite phase transformation) +ultrafast accelerated cooling could guarantee very fine microstructure and excellent mechanical properties. The X90 pipeline steel developed in WISCO has a good match of high strength and excellent toughness. Mechanical properties of X90 coils, plates and corresponding SSAW and LSAW pipes comprehensively meet the technical requirements of China National Petroleum Corporation (CNPC).
Authors: Qing Feng Wang, X.P. Xiao, X.J. Chen, W. Chen
Abstract: In this paper, an ultra-fine grained AZ31 magnesium alloy sheet with grain size less than 3μm was generated by three-run accumulative roll bonding of as cast alloy at a deformation temperature of 350°C and a reduction of 80% for each pass. The microstructures on the different ARB stages were observed and superplasticity examination in the ultrafine grained AZ31 alloy were carried out at a fixed temperature of 300°C and varied strain rate ranging from 10-4 to 10-1 s-1. It is indicated that significant grain refinement was mainly achieved in the first run and gradual uniformity of grain size in the next by continuous dynamic recrystalization. Besides, a superplastic deformation with a moderate elongation-to-fracture of 316% was obtained at a strain rate of 10-2 s-1 indicating a low temperature and high strain rate superplasticity, while a maximum elongation-to-fracture of 562% at10-4 s-1. The strain rate sensitivity exponent as high as of 0.34-0.41 implies the dominant role of grain boundary sliding in superplastic deformation at strain rate ranging from 10-3 to 10-2 s-1. The results indicate a possible approach to produce magnesium alloy sheet with fine grain and excellent deep drawing workability.
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