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Role of extrusion rate on the microstructure and tensile properties evolution of ultrahigh-strength low-alloy Mg-1.0Al-1.0Ca-0.4Mn(wt.%)alloy

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Journal of Magnesium and Alloys 2023年第2期11卷 553-561页

作者： X.Q.liu X.G.Qiao R.S.Pei y.Q.Chi L.yuan M.y.Zheng School of Material Science and Engineering Harbin Institute of TechnologyHarbin 150001China Institut fur Metallkunde und Meterialphysik RWTH Aachen UniversityAachen D-52056Germany

Mg-1.0Al-1.0Ca-0.4Mn(AXM1104, wt.%) low alloy was extruded at 200 ℃ with an extrusion ratio of 25 and different ram speeds from 1.0 to 7.0 mm/s. The influence of extrusion rate on microstructure and mechanical properties of the AXM1104 alloy was systematically studied. With the increasing of extrusion rate, the mean dynamically recrystallized(DRXed) grain size of the low alloy and average particles diameter of precipitate second phases were increased, while the degree of grain boundary segregation and the intensity of the basal fiber texture were decreased. With the rising of extrusion rate from 1.0 to 7.0 mm/s, the tensile yield strength(TyS) of the as-extruded AXM1104 alloy was decreased from 445 MPa to 249 MPa, while the elongation to failure(EL) was increased from 5.0% to 17.6%. The TyS, ultimate tensile strength(UTS) and EL of the AXM1104 alloy extruded at the ram speed of 1.5 mm/s was 412 MPa, 419 MPa and 12.0%, respectively,exhibiting comprehensive tensile mechanical properties with ultra-high strength and excellent plasticity. The ultra-high TyS of 412 MPa was mainly due to the strengthening from ultra-fine DRXed grains with segregation of solute atoms at grain boundaries. The strain hardening rate is increase slightly with increasing extrusion speed, which may be ascribed to the increasing mean DRXed grain size with rising extrusion speed. The higher strain hardening rate contributes to the higher EL of these AXM1104 samples extruded at higher ram speed.

关键词： Mg-Al-Ca-Mn alloy Ultrafine grain Extrusion rate Grain boundary segregation Microstructure Ultrahigh strength

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Proton therapy in clinical practice

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Chinese Journal of Cancer 2011年第5期30卷 315-326页

作者： Hui liu Joe y. Chang Sun yat-sen University Cancer Center Guangzhou Guangdong 510060 P. R. China Radiation Oncology Department University of Texas MD Anderson Cancer Center Houston TX 77030 USA

Radiation dose escalation and acceleration improves local control but also increases toxicity.Proton radiation is an emerging therapy for localized cancers that is being sought with increasing frequency by patients.Compared with photon therapy,proton therapy spares more critical structures due to its unique physics.The physical properties of a proton beam make it ideal for clinical applications.By modulating the Bragg peak of protons in energy and time,a conformal radiation dose with or without intensity modulation can be delivered to the target while sparing the surrounding normal tissues.Thus,proton therapy is ideal when organ preservation is a priority.However,protons are more sensitive to organ motion and anatomy changes compared with photons.In this article,we review practical issues of proton therapy,describe its image-guided treatment planning and delivery,discuss clinical outcome for cancer patients,and suggest challenges and the future development of proton therapy.

关键词：质子束临床实践治疗 Bragg峰辐射剂量物理特性局部控制癌症病人

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A method for solving relative dispersion of the cloud droplet spectra

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Science China Earth Sciences 2015年第5期58卷 929-938页

作者： Liu Yu LI WeiLiang Chinese Academy of Meteorological Sciences

The relative dispersion of the cloud droplet spectra or the shape parameter is usually assumed to be a constant in the two-parameter cloud microphysical scheme, or is derived through statistical analysis. However, observations have revealed that the use of such methods is not applicable for all actual cases. In this study, formulas were derived based on cloud microphysics and the properties of gamma function to solve the average cloud droplet radius and the cloud droplet spectral shape parameter. The gamma distribution shape parameter, relative dispersion, and cloud droplet spectral distribution can be derived through solving the droplet spectral shape parameter equation using the average droplet radius, volume radius, and their ratio, thereby deriving an analytic solution. We further examined the equation for the droplet spectral shape parameter using the observational droplet spectral data, and results revealed the feasibility of the method. In addition, when the method was applied to the two-parameter cloud microphysical scheme of the Weather Research and Forecast(WRF) model to further examine its feasibility, the modeling results showed that it improved precipitation simulation performance, thereby indicating that it can be utilized in two-parameter cloud microphysical schemes.

关键词：分散方法云滴谱 Gamma分布形状参数平均半径种用频谱形状参数方程

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Turbulence and mixing in a freshwater-influenced tidal bay: Observations and numerical modeling

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Science China Earth Sciences 2015年第7期58卷 2049-2058页

作者： LIAN Qiang liu Zhiyu Department of Physical Oceanography College of Ocean & Earth Sciences Xiamen University State Key Laboratory of Marine Environmental Science Xiamen University

In situ observations and numerical simulations of turbulence are essential to understanding vertical mixing processes and their dynamical controls on both physical and biogeochemical processes in coastal embayments. Using in situ data collected by bottom-mounted acoustic Doppler current profilers(ADCPs) and a free-falling microstructure profiler, as well as numerical simulations with a second-moment turbulence closure model, we studied turbulence and mixing in the Xiamen Bay, a freshwater-influenced tidal bay located at the west coast of the Taiwan Strait. Dynamically, the bay is driven predominantly by the M2 tide, and it is under a significant influence of the freshwater discharged from the Jiulong River. It is found that turbulence quantities such as the production and dissipation rates of the turbulent kinetic energy(TKE) were all subject to significant tidal variations, with a pronounced ebb-flood asymmetry. Turbulence was stronger during flood than ebb. During the flooding period, the whole water column was nearly well mixed with the depth-averaged TKE production rate and vertical eddy viscosity being up to 5?10?6 W kg?1 and 2?10?2 m2 s?1, respectively. In contrast, during the ebb strong turbulence was confined only to a 5?8 m thick bottom boundary layer, where turbulence intensity generally decreases with distance from the seafloor. Diagnosis of the potential energy anomaly showed that the ebb-flood asymmetry in turbulent dissipation and mixing was due mainly to tidal straining process as a result of the interaction between vertically shared tidal currents and horizontal density gradients. The role of vertical mixing in generating the asymmetry was secondary. A direct comparison of the modeled and observed turbulence quantities confirmed the applicability of the second-moment turbulence closure scheme in modeling turbulent processes in this weakly stratified tidally energetic environment, but also pointed out the necessity of further refinements of the model.

关键词：数值模拟混合过程湍流模型原位观测淡水垂直涡动粘性系数生物地球化学过程潮汐变化

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Association of farnesyl diphosphate synthase polymorphisms and response to alendronate treatment in Chinese postmenopausal women with osteoporosis

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Chinese Medical Journal 2014年第4期127卷 662-668页

作者： Liu Y Li M Zhou PR Xing XP Xia WB Xu L liu H J Zhang ZL LiaoEy Chen DC liu J Tao TZ Wu W Department of Endocrinology Key Laboratory of EndocrinologyMinistry of HealthPeking Union Medical College Hospital Peking Union Medical College Chinese Academy of Medical Sciences Beijing 100730 China Department of Endocrinology People&#39 s Hospital of Liaocheng Liaocheng Shandong 252002 China Metabolic Bone Disease and Genetics Research Unit Department of Osteoporosis and Bone Diseases Shanghai Sixth People&#39 s Hospital Affiliated with Shanghai Jiao Tong University Shanghai 200233 China Osteoporosis and Bone Diseases Shanghai Sixth People's HospitalAffiliated with Shanghai Jiao Tong University Shanghai 200233China Institute of Endocrinology and Metabolism Second Xiangya Hospitalof Central South University Changsha Hunan 410011 China Department of Endocrinology Osteoporosis Education Center WestChina Hospital Sichuan University Chengdu Sichuan 610041China Department of Orthopedics Xijing Hospital Fourth Liberation ArmyUniversity Xi'an Shannxi 710032 China Department of Orthopedics Harbin Medical University AffiliatedSecond Hospital Harbin Heilongjiang 150081 China Department of Endocrinology Guangdong General HospitalGuangzhou Guangdong 510080 China

Background Genetic factors are important in the pathogenesis of osteoporosis,but less is known about the genetic determinants of osteoporosis treatment.We aimed to explore the association between the gene polymorphisms of key enzyme farnesyl diphosphate synthase （FDPS） in mevalonate signaling pathway of osteoclast and response to alendronate therapy in osteoporotic postmenopausal women in China.Methods The study group comprised 639 postmenopausal women aged （62.2＆#177;7.0） years with osteoporosis or osteopenia who had been randomly assigned to low dose group （70 mg/2w） or standard dose group （70 mg/w） of alendronate in this 1-year study.We identified allelic variant of the FDPS gene using the polymerase chain reaction and restriction enzyme Faul.Before and after treatment,serum levels of calcium,phosphate,alkaline phosphatase （ALP）,cross linked C-telopeptide of type Ⅰ collagen （β-CTX） were detected.Bone mineral density （BMD） at lumbar spine and proximal femur was measured.The association was analyzed between the polymorphisms of FDPS gene and the changes of BMD,bone turnover biomarkers after the treatment.Results The FDPS rs2297480 polymorphisms were associated with baseline BMD at femoral neck,and patients with CC genotype had significantly higher baseline femoral neck BMD （（733.6＆#177;84.1） mg/cm2） than those with AC genotypes （（703.0＆#177;86.9） mg/cm2） and AA genotypes （（649.8＆#177;62.4） mg/cm2）（P 〈0.01）.No significant difference in BMD at lumbar spine was observed among different genotypes of FDPS.The percentage change of serum ALP level was significantly lower in patients with CC genotype （-22.9%） than that in those with AC genotype （-24.1%） and AA genotype （-29.8%） of FDPS after 12 months of alendronate treatment （P 〈0.05）.Neither percentage change of BMD nor β-CTX level after alendronate treatment had association with FDPS genotype.Conclusions FDPS gene was probably a candidate gene to predict femoral neck BMD at baseline.FDPS gene alleles could predict change percentage of ALP after treatment of alendron

关键词： farnesyl diphosphate synthase polymorphism alendronate osteoporosis pharmacogenomics

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Effects of Nb content in Ti–Ni–Nb brazing alloys on the microstructure and mechanical properties of Ti–22Al–25Nb alloy brazed joints

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Journal of Materials Science & Technology 2017年第7期33卷 682-689页

作者： y.Wang X.Q.Cai Z.W.yang D.P.Wang X.G.liu y.C.liu Tianjin Key Lab of Advanced Joining Technology School of Materials Science and Engineering Tianjin University Tianjin 300072 China

Vacuum brazing was successfully used to join Ti-22Al-25Nb alloy using Ti-Ni-Nb brazing alloys prepared by arc-melting. The influence of Nb content in the Ti-Ni-Nb brazing alloys on the interfacial microstructure and mechanical properties of the brazed joints was investigated. The results showed that the interfacial microstructure of brazed joint consisted of B2, O, ？3, and Ti2 Ni phase, while the width of brazing seams varied at different Nb contents. The room temperature shear strength reached359 MPa when the joints were brazed with eutectic Ti40Ni40Nb20 alloy at 1180？C for 20 min, and it was321, 308 and 256 MPa at 500, 650 and 800？C, respectively. Cracks primarily initiated and propagated in ？3compounds, and partially traversed B2＋O region. Moreover, the fracture surface displayed typical ductile dimples when cracks propagated through B2＋O region, which was favorable for the mechanical properties of the brazed joint.

关键词： Ti-22Al-25Nb alloy Ti-Ni-Nb brazing alloy Nb content Microstructure Mechanical properties

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A novel Mg-Gd-y-Zn-Cu-Ni alloy with excellent combination of strength and dissolution via peak-aging treatment

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Journal of Magnesium and Alloys 2023年第2期11卷 720-734页

作者： y.H.liu Z.R.Zhang J.Wang y.Li H.X.Li L.y.Jia J.H.Wang J.S.Zhang State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China Dekai Intelligent Casting Co. Ltd.Hebei 072750China

Inferior absolute strength and dissolution properties are the main bottlenecks for the widespread application of dissolvable magnesium alloys in complex working environments for unconventional oil and gas resources.Here,a novel functional peak-aged Mg-9.5Gd-2.7y-0.9Zn-0.8Cu-0.4Ni(wt.%) alloy for fracturing tools is reported,and it possesses an ultimate tensile strength of 457.6 MPa,ultimate compressive strength of 620.7 MPa and dissolution rate of ~43.7 mg·cm^(-2)·h^(-1) in 3 wt.% KCl solutions at 93℃.The excellent strength of the agedalloy is primarily attributed to the combination of grain refinement,long-period stacking ordered(LPSO) strengthening,and precipitation strengthening induced by stacking fault and β’ phase,among which the precipitation strengthening is dominant.Further investigations confirm that the corrosion is triggered from the micro-galvanic coupling between the Mg matrix and the cathodic lamellar and block LPSO phases.Strip-shaped corrosion pits along with LPSO phases are subsequently formed,significantly accelerating corrosion.The β’ precipitates can effectively improve the strength without compromising the dissolution rate because of their nanoscale size.This study provides an excellent material selection for dissolvable fracturing tools and presents a strategy by which a synergistic combination of strength and dissolution rate is achieved via peak-aging treatment.

关键词： Dissolvable magnesium alloy Peak-aging treatment Mechanical properties Micro-galvanic corrosion

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Efficacy of proximal tibial epiphyseal plate lengthening for tibial shortening deformity after opera⁃ tion for congenital pseudoarthrosis of the tibia in children

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Chinese Journal of Pediatric Surgery 2024年第5期45卷 436-440页

作者： Liu Y. liu K. Tan Q. Zhu G. Zhao W. yang G. Wu J. yi y. Xie y. Mei H. The Affiliated Children’s Hospital of Xiangya School of Medicine Central South University (Hunan Children’s Hospital) Hunan Provincial Key Laboratory of Pediatric Orthopedics The School of Pediatrics University of South China Changsha 410007 China

Objective To evaluate the healing efficacy and complications of proximal tibial epiphyseal plate lengthening with Ilizarov external fixation device in children with congenital pseudarthrosis of the tibia(CPT). Methods From June 2018 to October 2021,the relevant clinical data were retrospectively reviewed for 11 CPT children undergoing proximal epiphyseal plate lengthening surgery for tibial shortening. There were 6 boys and 5 girls. Based upon the radiographic results at Month 1 post⁃operation,callus quality was evaluated according to the Li classification. Quality of callus in extended segment and complications were followed up. Results Average operative age was 8. 8 years,average follow⁃up period 34. 4 months and average length of extension 6. 5 cm. The incidence of decent callus morphological quality was 100%,healing index 52. 5 d/cm and average fixation time of external fixation device 319 days. There were needle tract infection(n=1)and ankle stiffness(n=1). The outcomes were tibial extension angulation deformity(n=1),ankle plantar flexion 20° deformity(n= 1),knee joint mobility restriction(n=1)and ankle valgus(n=2). Conclusion The osteogenic quality of proximal tibial epiphyseal plate lengthening is excellent. For CPT children with tibial shortening, tibial lengthening should be customized according to specific situations. © 2024 Chinese Medical Journals Publishing House Co.Ltd. All rights reserved.

关键词： Bony callus Child Congenital pseudoarthrosis of tibia Growth plate Tibia

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皮质脊髓投射决定触觉和神经病理性触痛的敏感性

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中国疼痛医学杂志 2019年第1期25卷 4-5,10页

作者：黄亚坤(译) 刘兴君(校) Liu Y Latremoliere A Li X 汕头大学医学院不详

当前的躯体感觉感知模型强调感觉信息加工处理的过程是从初级感觉神经元经脊髓再传递到大脑。人们普遍认为心理对感知的影响是发生在脑内某些局部区域。本文主要研究脊髓水平的感觉信息的传入是否直接接受来自大脑皮质的、自上而下的控... 详细信息

当前的躯体感觉感知模型强调感觉信息加工处理的过程是从初级感觉神经元经脊髓再传递到大脑。人们普遍认为心理对感知的影响是发生在脑内某些局部区域。本文主要研究脊髓水平的感觉信息的传入是否直接接受来自大脑皮质的、自上而下的控制。尽管皮质脊髓束(CST)传统上被视为主要运动通路,但是有一群源自初级和次级躯体感觉皮层的皮质脊髓神经元(CSN)通过CST轴突直接投射到脊髓背角。躯体感觉中CSN活性的降低或CST的横断都会选择性地损害小鼠对轻触觉刺激的行为反应,但不改变对伤害性刺激的行为反应。此外,以上对CSN的操控极大地减轻了外周神经病理性疼痛中由触觉引发的异常性疼痛(Allodynia)。触觉刺激可以激活躯体感觉CSN,进而通过其皮质脊髓投射促进通过轻触诱发的脊髓背角深层的胆囊收缩素阳性的中间神经元的活动。这种由触觉驱动的脊髓-皮质-脊髓前馈反射致敏环路对于在触觉诱发的异常性疼痛条件下募集脊髓伤害性神经元非常重要。以上研究结果表明,脊髓中正常和病理条件下的触觉信息处理过程直接接受来自皮层的操控,并为神经病理性疼痛的治疗开辟了新思路。

关键词：神经病理性疼痛皮质脊髓束触觉刺激大脑皮质投射躯体感觉皮层初级感觉神经元敏感性

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High-temperature fatigue strength of grain boundaries with different misorientations in nickel-based superalloy bicrystals

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Journal of Materials Science & Technology 2023年第23期154卷 94-106页

作者： D.F.Shi Z.J.Zhang y.H.yang y.Z.Zhou R.liu P.Zhang Z.F.Zhang Shi-changxu Innovation Center for Advanced Materials Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering University of Science and Technology of China Shenyang 110016 China

Nickel-based single-crystal superalloys are widely used in the manufacture of aeroengine turbine vanes for their excellent high-temperature performance. Low-angle grain boundaries (LAGBs) will be generated inevitably during their manufacture, which are often characterized by grain boundary misorientation (GBM) and will weaken the mechanical properties of superalloys. However, the relationship between GBM and the fatigue properties of superalloys at elevated temperatures has seldom been investigated due to the difficulty in the sample preparation and experiment process. Based on six kinds of bicrystals with different tilt LAGBs made by a second-generation single-crystal superalloy, the effects of misorientation on the grain boundary microstructure and fatigue properties (980 °C) of superalloys were studied systematically in this work. It is found that, with the increase of GBM, the GB precipitates combined with the cast micropores increase monotonically, accordingly both the fatigue life and fatigue strength decrease successively. Fatigue fracture observations show that the cracks of all the bicrystals initiated from the cast micropores at GBs, and then propagated along the GBs. Therefore, the coupling effect of cast micropores and GBM on the fatigue damage mechanisms of the bicrystals are evaluated according to their hindering degrees on the piled-up dislocations. Combining with a hysteresis energy model, a quantitative fatigue strength prediction model of superalloys is established and is well verified by abundant experimental data. This study could provide guidance for fatigue performance prediction and structural design of superalloys.

关键词： Superalloys Bicrystals Grain boundary misorientation Fatigue strength Fatigue crack

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