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Evading strength−ductility trade-off of GH605 alloy using magnetic field-assisted undercooling treatment

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Transactions of Nonferrous Metals Society of China 2024年第8期34卷 2575-2588页

作者： Yi-xuan HE Fan BU Zhang-chi BIAN Ming-xiu XIANG Meng-meng ZHOU Xu-dong liU Lei ZHU Jun WANG jin-shan li State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China Center of Advanced Lubrication and Seal Materials Northwestern Polytechnical UniversityXi’an710072China Collaborative Innovation Center of NPU Shanghai 201108China Institute of Superconducting Materials and Applied Technology Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Key Laboratory of Electrical Materials and Infiltration Technology Xi’an University of TechnologyXi’an 710048China

Undercooling solidification under a magnetic field(UMF)is an effective way to tailor the microstructure and properties of Co-based *** this study,by attributing to the UMF treatment,the strength−ductility trade-off dilemma in GH605 superalloy is successfully *** UMF treatment can effectively refine the grains and increase the solid solubility,leading to the high yield *** main deformation mechanism in the as-forged alloy is dislocation *** contrast,multiple deformation mechanisms,including stacking faults,twining,dislocation slipping,and their strong interactions are activated in the UMF-treated sample during compression deformation,which enhances the strength and ductility *** addition,the precipitation of hard Laves phases along the grain boundaries can be obtained after UMF treatment,hindering crack propagation during compression deformation.

关键词： undercooling treatment magnetic field GH605 alloy strengthening mechanisms

2019—2022年呼和浩特市空气质量变化趋势研究

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环境与健康杂志 2024年第8期41卷 698-701页

作者：金利山刘芳内蒙古工业大学资源与环境工程学院内蒙古呼和浩特010051

目的了解2019—2022年呼和浩特市环境空气质量变化情况,探讨不同时间(年、月、季以及周)尺度下的呼和浩特市污染物浓度变化趋势。方法收集2019年1月—2022年12月呼和浩特市空气质量指数(AQI)及PM_(2.5)、PM_(10)、CO、NO_(2)、O_(3)、SO... 详细信息

目的了解2019—2022年呼和浩特市环境空气质量变化情况,探讨不同时间(年、月、季以及周)尺度下的呼和浩特市污染物浓度变化趋势。方法收集2019年1月—2022年12月呼和浩特市空气质量指数(AQI)及PM_(2.5)、PM_(10)、CO、NO_(2)、O_(3)、SO_(2)浓度数据,分析不同时间尺度下的变化趋势。结果从污染物浓度年变化来看,2019—2022年呼和浩特市空气质量为优和良的天数占比上升,空气质量有明显提高,2020年以后AQI明显下降。从污染物浓度月变化来看,各污染物浓度月均值呈现冷季(10月—次年4月)高、暖季(5—9月)低的特点。从季节变化特征分析,PM_(2.5)与PM_(10)在四季均有较高浓度,夏季PM_(2.5)和PM_(10)浓度低,而春、秋、冬季浓度高。6种污染物浓度的周变化情况类似,周一周二持平或减小,周三略有升高,在周四附近出现峰值,在周五六日逐渐减低。结论应重点关注大气污染严重的季节和月份,加强污染控制,进一步推动呼和浩特空气质量的改善。

关键词：呼和浩特变化趋势空气质量指数污染物浓度

强磁场下Cu−Co难混溶合金凝固过程中晶体取向和性能的调控

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Transactions of Nonferrous Metals Society of China 2024年第6期34卷 1878-1892页

作者：魏晨李金山闫育洁贺一轩 Eric BEAUGNON 王军西北工业大学凝固技术国家重点实验室西安710072 Univ.Grenoble Alpes INSA ToulouseUniv.Toulouse Paul SabatierEMFLCNRSLNCMI38000 GrenobleFrance

对Cu50Co50合金在不同磁场强度下进行非平衡凝固实验,研究富钴相的取向、显微组织演化和磁性能。结果表明,凝固后相分离的棒状富钴相可以实现排列形态,在5 T强磁场下富钴相的晶体取向为111平行磁场方向。然而,发生二次液−液相分离的富... 详细信息

对Cu50Co50合金在不同磁场强度下进行非平衡凝固实验,研究富钴相的取向、显微组织演化和磁性能。结果表明,凝固后相分离的棒状富钴相可以实现排列形态,在5 T强磁场下富钴相的晶体取向为111平行磁场方向。然而,发生二次液−液相分离的富铜相的取向没有受到HMF的显著影响。在0 T磁场下凝固的合金表现出近磁各向同性行为,而在5 T磁场下凝固的合金则表现出磁各向异性行为。合金的饱和磁化强度略有增加,矫顽力相应降低,这与富钴晶体的取向演化行为密切相关。

关键词：强磁场显微组织演化铜钴合金相分离磁性能

Optimization of thermal processing parameters of Ti555211 alloy using processing maps based on Murty criterion

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Rare Metals 2016年第2期35卷 154-161页

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

Isothermal compression testing of Ti555211 titanium alloys was carried out at deformation temperatures from 750 to 950 °C in 50 °C intervals with a strain rate of0.001-1.000 s^（-1）. The high-temperature deformation behavior of the Ti555211 alloy was characterized by analysis of stress-strain behavior, kinetics and processing maps. A constitutive equation was formulated to describe the flow stress as a function of deformation temperature and strain rate, and the calculated apparent activation energies are found to be 454.50 and 207.52 k J mol^（-1）in the a b-phase and b-phase regions, respectively. A processing map based on the Murty instability criterion was developed at a strain of 0.7. The maps exhibit two domains of peak efficiency from 750 to 950 °C. A ＊60 % peak efficiency occurs at 800-850 °C/0.001-0.010 s^（-1）. The other peak efficiency of ＊60 % occurs at C950 °C/0.001-0.010 s^（-1）, which can be considered to be the optimum condition for high-temperature working of this ***, at strain rates of higher than 1.000 s^（-1）and deformation temperatures of 750 and 950 °C, clear process flow lines and bands of flow localization occur in the hightemperature deformation process, which should be avoided in Ti555211 alloy hot processing. The mechanism in stability domain and instability domain was also discussed.

关键词： Ti555211 titanium alloy High temperature Deformation behavior Processing maps

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

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

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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

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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

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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

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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