检索结果-南通市图书馆

Microstructure evolution of a new near-β titanium alloy:Ti555211 during high-temperature deformation

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2015年第11期34卷 757-763页

作者： Zhen An jin-shan li Yong Feng State Key Laboratory of Solidification Processing Northwestern Polytechnical University

The isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 ℃ in 50 ℃ intervals,with strain rate of 0.001-1.000 s-1and height reduction of 20%-60%.The effect of processing parameters（deformation temperature,strain rate and deformation degree） on the microstructure evolution and the microstructure variables was *** results show that the content of primary α phase decreases with the increase in deformation *** effect of strain rate on microstructure variables of isothermally compressed Ti555211 alloy is mainly dependent on the deformation *** fine second α phase partly transforms to β phase due to the deformation heat effect at the high strain rate,α phase becomes globular with temperature increasing and strain rate *** contrast,α phase is refined with temperature decreasing and strain rate *** deformation degree has a little influence on the grain size and the morphology of primary α phase,but the effect of deformation degree on the morphology of second α phase is *** larger deformation degree is in favor of the globularization of lamellar α structure.

关键词： Titanium alloy High-temperature deformation Micros

Effect of order–disorder transition on thermodynamic and electronic properties of σ and χ phases in W–Re alloy: the first-principles calculation

在线全文

学校读者我要写书评

暂无评论

Tungsten 2025年第1期 195-213页

作者： Zhi-Peng Zhu Dian Jia William Yi Wang Jun-Lei Yin Xing-Yu Gao Shu-Feng Yang Hai-Feng Song jin-shan li State Key Laboratory of Solidification Processing Northwestern Polytechnical University Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics School of Metallurgical and Ecological Engineering University of Science and Technology Beijing

The Tungsten-Rhenium(W-Re) alloys,celebrated for their high melting point,strength at elevated temperatures,electrical resistivity,and radiation resistance,have been widely utilized in high-temperature components,aerospace,electronics,and nuclear *** constituents of the topologically close-packed(TCP) phases,the sigma phase(σ) and chi phase(χ) formed within W-Re alloys wield considerable influence on the mechanical properties and the stability of the *** calculations were utilized in the present work to explore the structural,thermodynamic,and electronic properties of both ordered and disordered configurations within the σ and χ phases,culminating in a systematic elucidation of the higher phase stability exhibited by the ordered *** is found that the bulk modulus of these two phases is directly proportional to the concentration of Re in the alloy,while the equilibrium volume is inversely *** thermodynamic parameters of the σ and χ phases are calculated via the mean-field potential *** similar trends observed in the isobaric heat capacity,enthalpy increment,and entropy change curves for these two phases suggest they possess comparable thermodynamic *** is noteworthy that the contribution of ionic vibrations predominantly affects the isobaric heat capacity,while the contribution of thermal electronic excitations increases linearly with *** the structure and thermodynamic properties of TCP phases in W-Re alloys at low temperatures has profound significance for optimizing material performance,microstructures features,establishing theoretical foundations,and predicting material behavior.

关键词：

Effect of Nb Content on Solidification Characteristics and Microsegregation in Cast Ti-48Al-xNb Alloys

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2016年第8期29卷 714-721页

作者： Tan He Rui Hu Tie-Bang Zhang jin-shan li State Key Laboratory of Solidification Processing Northwestern Polytechnical University

Microstructural evolution in nonequihbrium solidification of Ti-48Al-xNb alloys with Nb contents ranging from2 to 8 at%has been studied by containerless electromagnetic *** drops of controlled undercooling were quenched onto chill copper substrates and subjected to phase and microstructure *** increasing Nb content,the solidification path changes gradually from hyperperitectic solidification to hypoperitectic solidification and both solidification segregation（S-segregation） and β-solidification gradually increase.A transition from typical hypoperitectic solidification to a sole solidification of the β phase beyond a critical undercooling is revealed for the Ti-48Al-8Nb hypoperitectic *** the Ti-48Al-2Nb alloy,the morphologies of the primary β dendrites are not *** increasing undercooling,the coarsening of the lamellar colonies occurs,which can be attributed to the transition of the primary β dendritic ***,the solute concentration profiles for the final solidification microstructure are obtained to examine the segregation behaviors of alloying *** increasing Nb content,the undercooling eliminating S-segregation gradually increases.

关键词： TiAl alloy Undercooling Microsegregation Microstructure

Improved tensile properties of Al_(0.5)CoCrFeNi high-entropy alloy by tailoring microstructures

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2021年第9期40卷 2508-2513页

作者： Si-Zhe Niu Hong-Chao Kou Jun Wang jin-shan li State Key Laboratory of Solidiﬁcation Processing Northwestern Polytechnical UniversityXi’an 710072China

The effect of heat treatment on microstructure and tensile properties of as-cast Al_(0.5)CoCrFeNi high-entropy alloy was investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM) equipped with energy-dispersive spectroscopy(EDS), and tensile *** results show that heat treatment strongly affects the microstructure, particularly the morphology of bcc phases,and improves tensile properties. Microstructure analysis reveals that rod-shaped and elliptoid phases appear in the matrix after heat treatment at 1150 ℃. Besides, under850 ℃ heat-treated condition, ultimate tensile strength increases by about 60% without sacrificing much plasticity,which can be attributed to the content of bcc phases and fine precipitates dispersed in the dendrites. For other heattreated conditions, tensile ductility increases by at least30%, especially 60% for heat treatment at 450 ℃, and strength also improves. Fracture analysis indicates that the fracture mode of heat treatment at 850 ℃ is a mixture of quasi-cleavage and ductile fracture, while the other heattreated conditions show the mode of ductile fracture.

关键词： High-entropy alloys Heat treatment Microstructure Tensile properties

Effect of groove rolling on the microstructure and properties of Cu–Nb microcomposite wires

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and Materials 2021年第2期28卷 279-284页

作者： Peng-fei Wang Ming liang Xiao-yan Xu Jian-qing Feng Cheng-shan li Ping-xiang Zhang jin-shan li School of Materials Northwestern Polytechnical UniversityXi’an 710072China Northwest Institute for Nonferrous Metal Research Xi’an 710016China

Cu–Nb microcomposite wire was successfully prepared by a groove rolling *** effects of groove rolling on the diffraction peaks,microstructure,and properties of the Cu–Nb microcomposite were investigated and the microstructure evolutions and strengthening mechanism were *** tensile strength of the Cu–Nb microcomposite wire with a diameter of 2.02 mm was greater than 1 GPa,and its conductivity reached 68%of the International Annealed Copper Standard,demonstrating the Cu–Nb microcomposite wire with high tensile strength and high conductivity after groove *** results show that an appropriate groove rolling method can improve the performance of the Cu–Nb microcomposite wire.

关键词： groove rolling microstructure strengthening mechanism copper-niobium microcomposites

Effects of β-Dendrite Growth Velocity on β→a Transformation of Hypoperitectic Ti–46Al–7Nb Alloy

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2015年第1期28卷 58-63页

作者： Tan He Rui Hu Jun Wang Jie-Ren Yang jin-shan li State Key Laboratory of Solidification Processing Northwestern Polytechnical University

Solidification characteristics of Ti–46Al–7Nb melts were studied by the electromagnetic levitation technique.A maximum melt undercooling up to 240 K has been achieved. When the undercooling is lower than the critical value DT＊ = 205 K, the alloy possesses typical hypoperitectic solidification characteristic which can be evidenced by a peritectic layer observed in the as-solidified microstructure. However, the Widmansta¨tten structure can be observed at large undercooling regime of DT C DT＊, where peritectic reaction cannot proceed and c lamellar precipitation within a plates is suppressed. Based on the BCT dendrite growth model, the dendrite growth velocities were calculated as a function of undercooling. Theoretical analysis indicates that the growth mechanism of the primary b phase transforms from solutaldiffusion-controlled to thermal-diffusion-controlled in the undercooling range of 188–205 K, which can be attributed to the onset of solute trapping at the critical undercooling. Meanwhile, with increasing undercooling, the solute trapping effect becomes more dominant as a consequence.

关键词： TiAl alloy Dendrite growth Undercooling Microstructure

Soldering of Zr-based bulk metallic glass and copper by Au-12Ge eutectic alloy

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2019年第1期38卷 52-58页

作者： Jun Wang jing Cui Hong-Chao Kou Heng Guan jin-shan li State Key Laboratory of Solidification Processing Northwestern Polytechnical University

Zr-based bulk metallic glass and copper with different surface roughness were soldered using low temperature eutectic Au-12 Ge(wt%) solder on a thermomechanical simulator. The cross-sectional microstructures of the brazed joints were analyzed by scanning electron microscopy(SEM) and transmission electron microscope(TEM) in detail, and the compositional distribution along the interface was analyzed by energy-dispersive spectrometer(EDS). Results show that the surface roughness of base metals plays an important role in the quality of the brazed joint because the surface roughness can enlarge the effective contact area, which can improve the brazing surface quality between two materials. A moderate roughness of treated Zr-based metallic glass of 18 μm is shown to be the best for the soldering, while the surface roughness has a weak effect on the soldering behavior of Au-12 Ge solder on copper. After soldering, long-range diffusion of atoms occurs between the base metal and solder, and five distinct regions are formed at the joint region.

关键词： Bulk metallic glass Soldering Au-Ge eutectic alloy Interface

Calculation of the Physical and Microdosimetric Parameters of Electron and Alpha-Particle Radiation Using Monte Carlo Simulations

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2014年第3期31卷 181-183页

作者： GENG jin-Peng CAO Tian-Guang li Duo-Fang AN Hai-Long HAN Ying-Rong li jin HU jin-shan li Nan-Nan ZHAN Yong Institute of Biophysics School of Sciences Hebei University of Technology Tianjin 300401

Various ionizing radiations, such as electrons and alpha particles, transfer their energy to media by produced secondary electrons and induce double- or single-strand break of DNA, which result in variable effects. To understand how the ionizing radiations interact with DNA and break it, several models have been developed, most of them consider the water as a vapor state. Actually, the ionizing particles interact with DNA which is solved in liquid water. To compare the difference of vapor and liquid water models, we calculate the stopping power, continuous slowing down approximation （CSDA） range and S value of electrons and alpha particles at cellular scale in liquid and vapor by Monte Carlo simulations, respectively. Our data show that the stopping power and CSDA range are different in liquid and vapor water in a special energy range. For many S values, the liquid model is better than the vapor model when the energy of the electrons is higher than 100 keV and the vapor model is higher than the liquid model for the 1 MeV alpha particles.

关键词： MICRODOSIMETRY RESEARCH ELECTRONS -- Research RADIATION NUCLEAR cluster model MONTE Carlo method

Transition of solidification path in nonequilibrium solidification of Ti–48Al–8Nb alloy

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2016年第1期35卷 48-53页

作者： Tan He Rui Hu Jie-Ren Yang Tie-Bang Zhang jin-shan li The State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical University

The solidification behavior of Ti-48Al-8Nb alloy under nonequilibrium solidification conditions was studied by electromagnetic levitation *** solidification conditions are different undercooling（△T）under the same cooling condition and different cooling methods at the same undercooling condition,*** different undercooling conditions,when the undercooling is above a critical value（△T＊≈211K）,a remarkable morphological transition from typical hypoperitectic solidification to a sole solidification of the（3 phase resulting in the suppression of the peritectic reaction *** melts with different cooling conditions at the same undercooling（△T≈85 K）,the melt was rapidly cooled by quenching them in cooling *** cooling rate increasing,a transition from β phase to peritectic α phase solidification mode is revealed for Ti-48Al-8Nb alloy.

关键词： TiAl alloy Undercooling Nonequilibriumsolidification Microstructure evolution