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Thermal properties of high-k Hf_(1-x)Si_xO_2

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Chinese Physics B 2012年第7期21卷 431-438页

作者：司凤娟路文江汤富领 State key laboratory of Gansu Advanced non-ferrous metal Materials Department of Materials Science and EngineeringLanzhou University of Technology key laboratory of non-ferrous metal alloys and processing of Ministry of Education Lanzhou University of Technology

Classical atomistic simulations based on the lattice dynalnics theory and the Born core-shell model are performed to systematically study the crystal structure and thermal properties of high-k Hfl-xSixO2. The coefficients of thermal expansion, specific heat, Griineisen parameters, phonon densities of states and Debye temperatures are calculated at different temperatures and for different Si-doping concentrations. With the increase of the Si-doping concentration, the lattice constant decreases. At the same time, both the coefficient of thermal expansion and the specific heat at a constant volume of Hf1-mSixO2 also decreases. The Griineisen parameter is about 0.95 at temperatures less than 100 K. Compared with Si-doped HfO2, pure HfO2 has a higher Debye temperature when the temperature is less than 25 K, while it has lower Debye temperature when the temperature is higher than 50 K. Some simulation results fit well with the experimental data. We expect that our results will be helpful for understanding the local lattice structure and thermal properties of Hf1-mSixO2.

关键词： thermal properties lattice structure high-k material

Surface reconstruction on stishovite SiO_2,HfO_2 and rutile TiO_2 (001)

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Chinese Physics B 2011年第2期20卷 389-394页

作者：汤富领岳瑞路文江 State key laboratory of Gansu Advanced non-ferrous metal Materials Department of Materials Science and EngineeringLanzhou University of Technology key laboratory of non-ferrous metal alloys and processing of Ministry of Education Lanzhou University of Technology

This paper systematically investigates the surface reconstruction processes and patterns on stishovite SiO2, HfO2 and rutile TiO2 （001） by using classical molecular dynamics. It is found that these three surfaces relax instead of reconstruction at 0 K, and have little possibility to reconstruct below 40 K. Above 40 K, surface reconstructions take place as collective atomic motion which can be speeded by higher temperature or compressed strain. Several reconstruction patterns with approximate surface energies are found, and electrostatic potentials on them are also provided in comparison with possible microscopic results.

关键词： surface reconstruction molecular dynamics oxides

Microstructure of nano precursors of La-Mg hydrogen storage alloy synthesized by sol-gel technology at different pH values

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Rare metals 2012年第5期31卷 466-469页

作者： WANG Dahui XIA Jihong ZHANG Sha key laboratory of non-ferrous metal alloys and processing of Ministry of Education Lanzhou University of Science and Technology Lanzhou 730050 China

Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.

关键词： pH value microstructure nano precursors sol-gel technology

On-line evaluating on quality of mild steel joints in resistance spot welding

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China Welding 2008年第4期17卷 33-38页

作者：张鹏贤陈剑虹 key laboratory of non-ferrous metal alloys and processing of Ministry of Education Lanzhou University of Technology State key laboratory of Gansu Advanced non-ferrous metal Materials Lanzhou University of Technology

A method was developed to realize quality evaluation on every weld-spot in resistance spot welding based on information processing of artificial intelligent. Firstly, the signals of welding current and welding voltage, as information source, were synchronously collected. Input power and dynamic resistance were selected as monitoring waveforms. Eight characteristic parameters relating to weld quality were extracted from the monitoring waveforms. Secondly, tensile-shear strength of the spot-welded joint was employed as evaluating target of weld quality. Through correlation analysis between every two parameters of characteristic vector, five characteristic parameters were reasonably selected to found a mapping model of weld quality estimation. At last, the model was realized by means of the algorithms of Radial Basic Function neural network and sample matrixes. The results showed validations by a satisfaction in evaluating weld quality of mild steel joint on-line in spot welding process.

关键词： resistance spot welding weld quality characteristic parameter quality evaluating Radial Basic Function neural network

Effect of Zn Vaporization on Wetting of Al-galvanized Steel in Cold metal Transfer Process

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Journal of Iron and Steel Research International 2016年第6期23卷 566-572页

作者： Qiao-li LIN Gao-jun MAO Qian HUANG Rui CAO Jian-hong CHEN State key laboratory of Advanced processing and Recycling of non-ferrous metal Lanzhou University of Technology

The wetting of galvanized steel by molten Al alloys was studied in the cold metal transfer process by the sessile drop method using a high speed video *** wetting behavior can be divided into two typical cases,trending of non-wetting by using small wire feeding speed and wetting by using large wire feeding *** Leidenfrost effect is caused by the volatilization of Zn,which is responsible for the former *** enhanced wettability of steel by Al and the weakening of the Leidenfrost effect are responsible for the latter *** is the destabilizing factor for Al-steel joining that needs to be avoided by a reasonable design of process.

关键词： wetting camera evaporation latter weakening trending feeding boiling joining metallic

Effects of novel self-inoculation method on microstructure of AM60 alloy

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China Foundry 2011年第1期8卷 121-126页

作者： Xing Bo Li Yuandong Ma Ying Hao Yuan State key lab. of Gansu Advanced non-ferrous metal Materials Lanzhou University of Technology Lanzhou 730050 China key lab. of non-ferrous metal alloys and processing Ministry of Education Lanzhou University of Technology Lanzhou 730050 China

A novel cast processing method,self-inoculation method (SIM),was *** process involves the addition of self-inoculant to melt,then pouring the melt to a mould through a multi-stream mixing cooling *** this paper,the process parameters were *** indicate that the melt treatment temperature,the amount of self-inoculant added,and the slope angle of the cooling channel are the key factors for SIM *** optimized parameters are that the melt treatment temperature is between 680 and 700°C;the addition of self-inoculant is between 5wt.% and 7wt.%;and the slope angle of the cooling channel is between 30° and 45°.Further analysis reveals that SIM changes the solidification microstructure of slurry by controlling the nucleation and growth of the primary phase in the melt.

关键词： AM60 alloy self-inoculation method multi-stream mixing cooling channel nucleation and growth

Microstructural evaluation and mechanical properties of 7075 aluminum alloy prepared by controlled diffusion solidification

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China Foundry 2019年第4期16卷 238-247页

作者： Xiong Yang Yuan-dong Li Xiao-mei Luo Hong-wei Zhou Qi-yong Cai Ming Li Ying Ma State key laboratory ofAdvanced processing and Recycling of non-ferrous metals Lanzhou University of Technology Lanzhou 730050 China key lab of non-ferrous metal alloys and processing Ministry of Education Lanzhou University of Technology L anzhou 730050 China

In the present work, 7075 aluminum alloy(Al-Zn-Mg-Cu) was produced by both conventional casting(CC) and controlled diffusion solidification(CDS) methods. Each sample was subjected to different heat-treatment conditions: as-cast, T4, and T6;and their microstructural and mechanical properties were investigated by optical microscopy(OM), scanning electron microscopy(SEM) and X-ray diffractometry(XRD). It was found that CDS promoted the formation of non-dendritic primary α-Al phase and reduced shrinkage porosity, thus resulting in improved mechanical properties. In addition, the eutectic phase of the CDS samples mainly consisted of T(Al-ZnMg-Cu) phase, which manifested a well-developed lamellar eutectic structure. However, in the CC samples, the T(Al-Zn-Mg-Cu) phase was composed of rod-like eutectics. Moreover, the θ(Al2 Cu) eutectic contents in the CC samples were greater than those in the CDS samples. Each element in the CC samples had an obvious change in the grain boundary, whereas the change in element content in the CDS samples was gradual. Therefore, the non-dendritic morphology of the primary phase and the presence of rod-like eutectics in the matrix of the CDS samples led to enhanced tensile strength and elongation under different heat treatment conditions.

关键词： primary α-Al phase eutectic phase solute atoms tensile strength elongation

Microstructure evolution and mechanical properties of 316L austenitic stainless steel with aluminum addition by warm rolling

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Journal of Iron and Steel Research International 2018年第10期25卷 1068-1077页

作者： Xin GUO Pei-qing La Heng Li Yu-peng Wei Xue-feng Lu State key laboratory of Advanced processing and Recycling of non-ferrous metal Lanzhou University of Technology Lanzhou 730050 Gansu China key laboratory of nonferrous metal alloys and processing Ministry of Education Lanzhou University of Technology Lanzhou 730050 Gansu China

Microstructure evolution and mechanical properties of 316L austenitic stainless steel with aluminum addition by warm rolling at 550 ℃ were investigated. It is found that sample is composed of an ashen austenite matrix, a gray black ferrite phase and a small number of NiCx. The average grain sizes are 21.62, 19.66 and 19.49 μm for samples with the rolling deformation of 30%, 50% and 70%, respectively. The yield strength and tensile strength of samples with solid solution time of 30 min and deformation of 70% are higher. The fracture modes are similar and belong to toughness fracture. The fracture surfaces of the samples are composed of relatively large equal-axis ductile dimples （5-15 μm） and fine scattered ones around the dimples （〈 5 μm）. As the rolling deformation increases, the quantity of subgrain boundary increases and the 〈 101 〉 orientation is more prominent. {001 } 〈 110 〉 rotation-cube textures are present in ferrite phase of samples and weak Goss texture is formed in austenite pole images.

关键词： AISI 316L austenitic stainless steel Warm rolling Tensile property Fracture mechanism Deformationtexture

Numerical analysis for weld pool of pulsed TIG welding

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China Welding 2013年第1期22卷 71-76页

作者：黄健康郭朝博黄琳石玗樊丁 key laboratory of non-ferrous metal alloys and processing The Ministry of Education Lanzhou University of Technology Lanzhou 730050 State key laboratory of Gansu Advanced non-ferrous metal Materials Lanzhou University of Technology Lanzhou 730050.

A two-dimensional axisymmetric mathematical model of weld pool of pulsed TIG welding was established. Numerical simulation for weld pool of pulsed TIG welding was done using FLUENT software by selecting the appropriate boundary conditions and strongly coupled control equations. The distributions of temperature field and flow field of weld pool under the periodic change of welding current were obtained. According to the maximum temperature of upper and lower surface of workpiece and depth and width of weld pool, the distributions of temperature field and flow field under different pulsed frequencies and current duty cycles were obtained and periodic variation was analyzed under pulsed current. The analysis results show that with the increase of pulsed frequency, weld pool width increases slightly while depth decreases slightly, and with the increase of current duty cycle, the width and depth of weld pool both increase significantly, and the depth increases greatly.

关键词： pulsed TIG welding weld pool numerical simulation FLUENT