Effect of Homogenization Temperature on Microstructure and Mechanical Properties of Low-Carbon High-Boron Cast Steel

Fu Hanguang,Song Xuding,Lei Yongping,Jiang Zhiqiang,Xing Jiandong,Yang Jun,Wang Jinhua 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.3

The effects of quenching treatment on the microstructure, hardness, impact toughness, and wear resistance of low-carbon high-boron cast steel (LCHBS) containing 0.15-0.3 %C, 1.4-1.8 %B, 0.3-0.8 %Si, 0.8-1.2 %Mn, 0.5-0.8%Cr, 0.3-0.6%Ni, and 0.3-0.6%Mo have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and via an electron probe microanalyzer (EPMA), X-ray diffraction (XRD) analysis, impact tester, hardness tester, and wear tester. The as-cast matrix of LCHBS consists of pearlite and ferrite. There is 8-10 vol.% Fe2(B, C) type borocarbides in the matrix. The micro-hardness of Fe2(B, C) is 1430-1480 Hv. Fe2(B,C) shows no obvious change and the matrix completely transforms into lath martensite upon quenching at 900 °C to 1100 °C. The microhardness of the matrix and the macrohardness of the LCHBS sample show a slight increase with an increase of homogenization temperature. When the homogenization temperature exceeds 1050 °C, no distinct change in the hardness is observed. The change of homogenization temperature has no apparent effect on the impact toughness of LCHBS. The mass losses of LCHBS increase distinctly when the wear load increases. The homogenization temperature is less than 1000 °C and the wear rate of LCHBS decreases with an increase of temperature. The wear rate does not display any obvious change after exceeding a homogenization temperature of 1000 °C. The effects of quenching treatment on the microstructure, hardness, impact toughness, and wear resistance of low-carbon high-boron cast steel (LCHBS) containing 0.15-0.3 %C, 1.4-1.8 %B, 0.3-0.8 %Si, 0.8-1.2 %Mn, 0.5-0.8%Cr, 0.3-0.6%Ni, and 0.3-0.6%Mo have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and via an electron probe microanalyzer (EPMA), X-ray diffraction (XRD) analysis, impact tester, hardness tester, and wear tester. The as-cast matrix of LCHBS consists of pearlite and ferrite. There is 8-10 vol.% Fe2(B, C) type borocarbides in the matrix. The micro-hardness of Fe2(B, C) is 1430-1480 Hv. Fe2(B,C) shows no obvious change and the matrix completely transforms into lath martensite upon quenching at 900 °C to 1100 °C. The microhardness of the matrix and the macrohardness of the LCHBS sample show a slight increase with an increase of homogenization temperature. When the homogenization temperature exceeds 1050 °C, no distinct change in the hardness is observed. The change of homogenization temperature has no apparent effect on the impact toughness of LCHBS. The mass losses of LCHBS increase distinctly when the wear load increases. The homogenization temperature is less than 1000 °C and the wear rate of LCHBS decreases with an increase of temperature. The wear rate does not display any obvious change after exceeding a homogenization temperature of 1000 °C.

Synthesis of Polyolefin In-Reactor Alloys by Periodic Switching Polymerization Process

Zhiqiang Fan,Biao Zhang,Zhisheng Fu,Junting Xu 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Preparation, characterization and CO oxidation activity of Cu-Ce-Zr mixed oxide catalysts via facile dry oxalate-precursor synthesis

Guangying Fu,Dongsen Mao,Shuaishuai Sun,Jun Yu,Zhiqiang Yang 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.31 No.-

CuO-CeO2-ZrO2 catalysts were prepared via facile dry oxalate-precursor synthesis and tested for COoxidation. The effect of Cu contents was investigated by N2 adsorption, TEM, XRD, XPS, H2-TPR, CO-TPDand Raman techniques. The results show that CuO dispersion, SBET and adsorbed CO amount exhibit avolcano trend with increasing the Cu content. The highest activity was achieved over the catalyst with18 mol% Cu with the CO conversion being 99% at 85 8C. The superior performance of the catalystprepared by this method is attributed to the finely dispersed CuO species and the strong interaction ofCuO with ceria-zirconia phase.

MODEL PREDICTIVE TRAJECTORY OPTIMIZATION AND TRACKING IN HIGHLY CONSTRAINED ENVIRONMENTS

Lu Xiong,Zhiqiang Fu,Zixuan Qian,Bo Leng,Dequan Zeng,Yanjun Huang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.4

This paper presents a model predictive trajectory optimization and tracking framework to avoid collisions for autonomous vehicles in highly constrained environments. Firstly, a vehicle model is established in road coordinate system to describe the relationship between the vehicle and the reference road. Secondly, a numerical optimization method is applied to smoothen the reference path generated by waypoints. Then, a multilayer searched method is used to establish a safe driving corridor in highly constrained environments. In addition, an optimal path optimization and tracking framework based on model predictive control is formulated to improve the driving safety and comfort. The proposed framework considers the constraints of path boundaries and vehicle dynamics to provide the optimal control command. Furthermore, the speed profile is optimized based on the longitudinal motion model in space domain to ensure the constraints of speed limits and vehicle acceleration. Finally, the proposed algorithms are evaluated through experiments in various scenarios to demonstrate the effectiveness.

Research on Dynamic Pressure of Hydrostatic Thrust Bearing Under the Different Recess Depth and Rotating Velocity

Xiaodong Yu,Zhiqiang Wang,Xiuli Meng,Huanhuan Li,Dan Liu,Xu Fu,Bo Wu,Li Tan,Bai Qin,Xuezhe Dong 보안공학연구지원센터 2014 International Journal of Control and Automation Vol.7 No.2

The Malleability of Culture and Leadership Style in East Asia

Ji Li,Ping Ping Fu,Zhiqiang Liu,Y.Y. Chen 한국조직경영개발학회 2008 조직경영개발연구 Vol.1 No.1

글로별 리더십과 조직행동유효성 프로그램 (GLOBE) 의 데이터를 분석하여 우리는 동아시아 국가들 사이에 문화와 리더십 스타일에 차이가 있다는 것을 발견하였다. 이런 차이를 설명하기 위하여 우리는 새로운 이론적 관점인 제도적 공생이라는 관점을 개발하였다. 생물학의 개념에 해당되는 이 제도적 공생의 관점은 상이한 개체 또는 종들이 어떻게 제도적 환경을 포함한 어떤 환경에서 함께 살아가게 되는지를 설명한다. 이 새로운 관점은 제도파 이론에서 보이는 한계들을 극복할 수 있게 한다. 또한 사회문화와 합법적 리더십 스타일을 포함한 사회제도의 동태적인 성격을 이해하는데 도움을 준다. 이 새로운 개념이 학자와 실무자들에게 주는 시사점으로 결론을 맺었다. Analyzing the data collected for the Global Leadership and Organizational Behavior Effectiveness Program (GLOBE), we found some interesting differences in culture and leadership style among economies in East Asia. To explain these differences, we develop a new theoretical perspective, institutional symbiosis. Developed from a similar concept in biology, the perspective of institutional symbiosis describes how different species or elements closely living together in a certain environment, including institutional environment. This new perspective helps overcome some limitations in the current literature of institutional theory. It can also improve our understanding of the dynamic nature of social institutions, including societal cultures and legitimate leadership style. The paper concludes with a discussion on the implications of this new perspective for researchers and practitioners.

A New Method of Active Center Determination for Olefin Polymerization with Supported Ziegler-Natta Catalysts

Letian Zhang,Zhisheng Fu,Zhiqiang Fan 한국고분자학회 2010 Macromolecular Research Vol.18 No.7

A novel method based on a reaction between the growing polymer chain and cinnamoyl chloride (CC)was developed to determine the number of active centers (Cp) in olefin polymerization with supported Ziegler-Natta catalysts. The reaction of titanium-polymeryl bonds in the active centers of MgCl2/ID/TiCl4-AlR3 type catalysts with CC was very fast at 20~80 oC. Cinnamoyl labeled polymer chains were formed, which were stable in the reaction system for at least 10 min when the CC/Al molar ratio was > 1. The number of active centers was determined by measuring the number of carbonyl groups in the polymer with the UV-vis method. The Cp values of the 1-hexene polymerization systems with the addition of hydrogen were also measured.

Synthesis of Polyethylene/Poly(ethylene-co-propylene) In-Reactor Alloys by Periodic Switching Polymerization Process: Effects of Switching Frequency on Polymer Structure and Properties

Yaobin Liu,Biao Zhang,Zhisheng Fu,Zhiqiang Fan 한국고분자학회 2017 Macromolecular Research Vol.25 No.6

In this work, a series of polyethylene/poly(ethylene-co-propylene) in-reactor alloys (PE/EPR) were synthesized with MgCl2-supported Ziegler-Natta catalyst by a three-stage reaction process including slurry ethylene homopolymerization, gasphase ethylene/propylene copolymerization and alternating homo- and copolymerization (PSPP stage), and the effects of switching frequency (SF) on their structure and properties were studied. The alloy was composed of random ethylene/propylene copolymer (EPR), segmented ethylene/propylene copolymer (EPS) and polyethylene (PE). Increasing SF in the PSPP stage led to significant changes in the composition, chain structure, mechanical properties and phase morphology of the alloys. By increasing SF from 1 to 30, the amount of EPR fraction slightly decreased then increased, but the EPS fraction significantly increased in a monotonous way. Increasing SF led to formation of EPS with longer PE sequence and higher crystallinity. The alloys showed much higher toughness at low temperature (-50 °C) than polyethylene. The alloy prepared at SF=6 showed better toughness-stiffness balance than those prepared under other conditions. The PE/EPR alloys showed typical sea-islands phase structure, with the EPR domains being the dispersion phase. The alloy prepared at SF = 6 showed EPR phases with the smallest size and the most uniform spacial distribution in the PE matrix. The observed improvements in alloys mechanical properties are explained by the enhancement of phase compatibility with increase in SF.

Structure of MnOx/TiO2 Catalysts and Their Catalytic Performance in the Gas-Phase Oxidation of o-Dichlorobenzene

Wenrui Zhang,Aidong Tang,Dabin Ren,Hui Xiang,Zhiqiang Yu,Guoying Sheng,Jiamo Fu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.5

The influence of structure of MnOx/TiO2 catalysts and their catalytic oxidation of o-dichlorobenzene were examined in this study. MnOx/TiO2 catalysts were characterized by X-ray diffractometer (XRD), thermogravimetry-differential thermal analysis (TG-DTA), TEM, X-ray photoelectron spectrum (XPS) and FTIR for NH3 adsorption techniques. Experimental results indicated that the MnOx/TiO2 catalyst prepared from manganese nitrate possessed the highest catalytic activity with a gas hourly space velocity (GHSV) of 14,500 h-1. This activity may be due to a large amount of surface Mn2O3 species, the strong Brönsted and Lewis acidity and the combined TiO2 phases. Additionally, a possible reaction model from o-dichlorobenzene oxidation over MnOx/TiO2 catalyst was suggested based on the analysis.

Uncovering Microstructure Evolution and Dynamic Softening Mechanism of Spray-Deposited AlZnMgCu Alloy Under Thermal Deformation

Guoai He,Cunxiao He,Yu Liu,Chao Liu,Zhiqiang Fu,Shuanghui Xu,Xiaofei Sheng,Zhu Xiao,Qinghong Wen 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.9

Dynamic softening behavior has been of great concern in the aluminum alloys, which served a vital role in affecting themicrostructure, deformation resistance and the final mechanical properties. In this paper, spray deposition was applied tomanufacture AlZnMgCu alloy to refine the casting microstructure and reduce segregation. The microstructure responses andcorresponding mechanism during the thermal compression with various temperatures and various strain rates were multiscalecharacterized and uncovered using high-resolution EBSD. The results revealed that many broken and fine grains wereobserved in the uneven and jagged grain boundaries under the low temperatures and high strain rates, which indicated theoccurrence of partial discontinuous dynamic recrystallization (DDRX). In addition, high density dislocations were formedat original grain boundaries, where great amount of low angle grain boundaries (LAGBs) were appeared. With temperatureincreased and strains rate decreased, the LAGBs would evolve to the high angle grain boundaries (HAGBs) owing to theconsiderable dislocations migrated to the grain boundaries then accumulated, which triggered the occurrence of continuousdynamic recrystallization (CDRX). Two different dynamic recrystallization types were observed and factors that influenceddifferent dynamic recrystallization behaviors were clearly elaborated, and the corresponding mechanism was indicateddetailly.