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A comparative study of the role of solute,potent particles and ultrasonic treatment during solidification of pure Mg,Mg-Zn and Mg-Zr alloys

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Journal of Magnesium and Alloys 2021年第3期9卷 829-839页

作者： Nagasivamuni Balasubramani Gui Wang mark a.easton David H.St John Matthew S.Dargusch Centre for Advanced Materials Processing and Manufacturing(AMPAM) School of Mechanical and Mining EngineeringThe University of QueenslandBrisbane 4072Australia School of Engineering RMIT UniversityCarlton3053 VICAustralia

Ultrasonic treatment(UST)applied during the solidification of pure Mg,eutectic(Mg-Zn)and peritectic(Mg-Zr)alloys was investigated in order to explore the grain refinement *** dependent grain refinement is observed in pure Mg where decreasing the superheat temperature(at which UST is applied from above the melting temperature,TM)from 100℃to 40℃produces significant refinement with a uniform grain *** presence of solute reduces the temperature dependence of the UST refinement and excellent grain refinement is obtained regardless of the superheat temperature(100℃or 40℃)and even with the use of preheated sonotrode in the Mg-6 wt.%Zn alloy.A further improvement in grain refinement is achieved when the alloy contains potent particles that introduce additional nucleation of grains in Mg-0.5 and 1.0 wt.%Zr alloys(producing an average grain size of≤100μm).At 40℃superheat,UST of Mg-Zn alloys produces excellent refinement(average grain size<200μm)with non-dendritic grains,which is normally achieved only with the addition of grain refining master alloy in the as-cast *** enhanced refinement observed in the eutectic alloy is explained through the undercooling imposed by a relatively cold sonotrode combined with high frequency vibrations and acoustic *** advantages of using a cold sonotrode,a low superheat and solute are demonstrated for achieving significant refinement during solidification of Mg alloys under UST without or with a lower addition of grain refining master alloys.

关键词： Grain refinement Mg-Zn alloy Mg-Zr alloy Ultrasonic treatment Interdependence Model Solidification

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Re-evaluation of the mechanical properties and creep resistance of commercial magnesium die-casting alloy AE44

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Journal of Magnesium and Alloys 2021年第5期9卷 1552-1560页

作者： Suming Zhu Trevor B.Abbott Jian-Feng Nie Hua Qian Ang Dong Qiu Kazuhiro Nogita mark a.easton School of Engineering RMIT UniversityCarltonVictoria 3053Australia Department of Materials Science and Engineering Monash UniversityVictoria 3800Australia Magontec Limited SydneyNew South Wales 2000Australia School of Mechanical and Mining Engineering The University of QueenslandSt LuciaQueensland 4072Australia

This paper presents a re-evaluation of the room temperature mechanical properties and high temperature creep resistance of magnesium die-casting alloy AE44(Mg-4Al-4RE)in light of the influence of minor Mn *** is shown that the Mn-containing AE44 exhibits distinct age hardening response upon direct ageing(T5)due to the precipitation of nanoscale Al-Mn particles,as reported previously in a similar *** T5 ageing leads to a significant improvement in strength with similar ***,the T5-aged AE44 has a remarkably better strength-ductility combination than most Mg die-casting alloys and even the Al die-casting alloy *** Mn addition is also shown to be critical for the creep resistance of AE44 whereas the influence of the RE constituent is not as significant as previously thought,which reaffirms that precipitation hardening of theα-Mg matrix is more important than grain boundary reinforcement by intermetallic phases for the creep resistance of die-cast Mg *** findings in this work could provide new application perspectives for AE44,particularly in the automotive industry.

关键词： Magnesium alloys Manganese Precipitation hardening Mechanical properties Creep Die casting

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Laser directed energy deposited, ultrafine-grained functional titanium-copper alloys tailored for marine environments: Antibacterial and anti-microbial corrosion studies

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Journal of Materials Science & Technology 2023年第35期166卷 21-33页

作者： Jiaqi Li Duyao Zhang Xiaobo Chen Dake Xu Dong Qiu Fuhui Wang mark easton Shenyang National Laboratory for Materials Science Northeastern UniversityShenyang 110819China Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) School of Materials Science and EngineeringNortheastern UniversityShenyang 110819China School of Engineering Centre for Additive ManufacturingRMIT UniversityMelbourneVIC 3000Australia

The microorganism-rich nature of the ocean imposes great challenges to the structural integrity of met-als over their service lifespan,including titanium(Ti)alloys,which are usually prone to microbiologically influenced corrosion(MIC).So,multifunctional anti-MIC Ti alloys need to be developed and *** paper investigates the effect of copper(Cu)concentration on the MIC resistance of a series of additively manufactured,ultrafine-grained Ti-x Cu(x=3.5,6.5 and 8.5 in wt.%)*** dependence of the cor-rosion resistance and MIC resistance on the Cu concentration of Ti-Cu alloy is interpreted considering all conceivable *** mechanisms for excellent corrosion resistance of Ti-Cu alloy in seawater are attributed to the strong passive film and small surface potential difference between ***-tural characterization reveals that uniformly distributed,nanosized Ti_(2) Cu phase led to increased reactive oxygen species in the bacterial membrane,which is the root reason for the superb anti-bacterial property(99.2%)for *** to pure Ti and Ti-6Al-4V,Ti-8.5Cu alloy features both high strength(yield stress>1000 MPa)and the best MIC resistance(97.5%).The combination of such balanced properties enables this functional 3D printed Ti-Cu alloy to become an ideal material for load-bearing applications in the marine environment.

关键词： Multifunctional titanium alloys Additive manufacturing Ultrafine grains Microbiologically influenced corrosion resistance Mechanical property Antibacterial property

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Recent advances in biodegradation controls over Mg alloys for bone fracture management: A review

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Journal of Materials Science & Technology 2019年第4期35卷 535-544页

作者： Ming-Shi Song Rong-Chang Zeng Yun-Fei Ding Rachel W.Li mark easton Ivan Cole Nick Birbilis Xiao-Bo Chen School of Engineering RMIT University Department of Materials Science and Engineering Monash University College of Materials Science and Engineering Shandong University of Science and Technology School of Mechanical Engineering Huaihai Institute of Technology The Medical School The Australian National University

Magnesium(Mg) alloys possess comparable physical and mechanical properties to bone, making them an outstanding candidate of implant materials for bone fracture treatment. In addition to the excellent biocompatibility, and bioactivity, the engagement of Mg alloys is key for a number of biological functionalities in the human body. The unique biodegradation nature of Mg alloy implants implies that it may not require a secondary removal procedure when the expected supporting tasks accomplish, as they may simply and safely "disappear" over time. Nonetheless, the demonstrated drawback of potentially rapid degradation, is an issue that must be addressed appropriately for Mg implants and is consequently given unique attention in this review article. Herein, the critical criteria and the state-of-the-art strategies for controlling the degradation process of Mg alloys are reported. Furthermore, future developments of biodegradable Mg and its alloys systems with satisfactory specifications for clinical trials and deployment,are discussed. This review aims to provide information to materials scientists and clinical practitioners in the context of developing practical biodegradable Mg alloys.

关键词： Magnesium alloys Biodegradation Corrosion mechanisms Cytocompatibility

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Crystallographic study of Al_3Zr and Al_3Nb as grain refiners for Al alloys

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Transactions of Nonferrous Metals Society of China 2014年第7期24卷 2034-2040页

作者：汪锋邱冬刘峙麟 John TAYLOR mark easton 张明星 School of Mechanical and Mining Engineering The University of Queensland School of Physics and Materials Engineering Monash University

The potency of Al3Zr and Al3Nb as grain refiners for Al alloys was investigated from a crystallographic point of view using the edge-to-edge matching （E2EM） model. The results show that both Al3Zr and Al3Nb have small values of interatomic spacing misfit and interplanar spacing mismatch with respect to Al. Furthermore, energetically favourable orientation relationships predicted by the model exist between Al and each of these two intermetallic phases. In the light of the edge-to-edge matching model predictions, it is suggested that both Al3Zr and Al3Nb are potent heterogeneous nucleation refiners for Al grains from the crystallographic point of view. The present crystallographic analysis provides a more reasonable explanation for the significant grain refinement obtained in the peritectic Al-Zr and Al-Nb alloys and also provides fresh insight into the understanding of the grain refinement mechanism of Al alloys.

关键词： Al alloy A3Zr Al3Nb grain refinement peritectic crystallography E2EM model

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Effect of Inoculation on Phase Formation and Indentation Hardness Behaviour of Zr47.5Cu45.5Al5Co2and Zr65Cu15Al10Ni10Bulk Metallic Glass Matrix Composites

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Engineering（科研） 2018年第8期10卷 530-559页

作者： Muhammad Musaddique Ali Rafique Milan Brandt mark easton RMIT University Carlton VIC Australia

Bulk metallic glass matrix composites have emerged as a new potential material for structural engineering applications owing to their superior strength, hardness and high elastic strain limit. However, their behaviour is dubious. They manifest brittleness and inferior ductility which limit their applications. Various methods have been proposed to overcome this problem. Out of these, introduction of foreign particles (inoculants) during solidification has been proposed as the most effective. In this study, an effort has been made to delimit this drawback. A systematic tale has been presented which explains the evolution of microstructure in Zr47.5Cu45.5Al5Co2 and Zr65Cu15Al10Ni10 bulk metallic glass matrix composites with varying percentage of ZrC inoculant as analysed by secondary electron, back scatter electron imaging of “as cast” unetched samples and indentation microhardness testing. Secondary electron imaging of indents was also performed which shows development of shear transformation zones at edges of square of indents. Mostly, no cracking was observed, few cracks bearing Palmqvist morphology were witnessed in samples containing lower percentage of inoculant. A support is provided to hypothesis that inoculations remain successful in promoting phase formation and crystallinity and improving toughness.

关键词： Inoculation Crystallinity Phase Formation Toughness

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Effect of Single Pass Laser Surface Treatment on Microstructure Evolution of Inoculated Zr47.5Cu45.5Al5Co2and Non-Inoculated Zr65Cu15Al10Ni10Bulk Metallic Glass Matrix Composites

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Engineering（科研） 2018年第10期10卷 730-758页

作者： Muhammad Musaddique Ali Rafique Milan Brandt mark easton Ivan Cole Sabu John School of Engineering RMIT UniversityMelbourneAustralia Additive Manufacturing Precinct RMIT UniversityMelbourneAustralia Advanced Manufacturing and Fabrication Enabling Capability Platform RMIT UniversityCity CampusMelbourneAustralia School of Engineering Cluster Manufacturing Materials and MechatronicsRMIT UniversityBundoora CampusMelbourneAustralia

Bulk metallic glass matrix composites are advocated to be material of future owing to their superior strength, hardness and elastic strain limit. However, they possess poor toughness which makes them unusable in any structural engineering application. Inoculation has been used as effective mean to overcome this problem. Zr47.5Cu45.5Al5Co2 bulk metallic glass matrix composites (BMGMC) inoculated with ZrC have shown considerable refinement in microstructure owing to heterogeneous nucleation. Efforts have also been made to exploit modern laser-based metal additive manufacturing to fabricate BMGMC parts in one step. However, the effect of laser on inoculated material is unknown. In this study, an effort has been made to apply single pass laser surface treatment on untreated and inoculated BMGMC samples. It is observed that laser treatment not only refine the microstructure but result in change of size, morphology and dispersion of CuZr B2 phase in base metal, heat affected zone and fusion zone in Zr47.5Cu45.5Al5Co2. A similar effect is observed for β-Zr and Zr2Cu in non-inoculated Zr65Cu15Al10Ni10. This effect is documented with back scatter electron imaging.

关键词： Additive Bulk Metallic Glass Composites Inoculation Phase

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论董事会改革与权益资本成本：国际证据

论董事会改革与权益资本成本：国际证据

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作者： mark Nyamekye Atta 厦门大学

学位级别：硕士

利用在1990-2012年间进行了公司董事会改革的41个国家的样本,本文运用双重差分(difference-in-difference)模型研究了该改革对公司权益资本成本的影响。沿用easton(2004)的做法,本文运用基于分析师盈余预测与股票价格的PEG模型来衡量公... 详细信息

利用在1990-2012年间进行了公司董事会改革的41个国家的样本,本文运用双重差分(difference-in-difference)模型研究了该改革对公司权益资本成本的影响。沿用easton(2004)的做法,本文运用基于分析师盈余预测与股票价格的PEG模型来衡量公司的隐含资本成本。基于上述方法,本文发现董事会改革降低了企业权益资本成本,该效应在运用遵守或解释方法(comply-or-explain approach)的国家比在运用基于规则方法(rule-based approach)的国家更加显著。类似地,相较于大陆法系国家,这种效应在普通法系国家更加显著。另外,本文分析了改革所涉及的各个部分,并发现涉及董事会独立性、审计委员会与审计独立性、和董事长与总经理两职分离的改革才会降低权益成本,而没有证据表明不涉及上述内容的改革也会有这种效应。进一步的稳健性检验使用了权益资本成本的不同衡量方法,且使用不同样本量的样本,上述结论仍旧不变。

关键词：董事会改革权益资本成本隐含资本成本分析师盈余预测

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短暂性脑缺血发作的定义和评价:美国心脏协会/美国卒中协会卒中委员会、心血管外科和麻醉委员会、心血管放射学和介入委员会、心血管护理委员会和外周血管病跨学科委员会对医疗卫生专业人员发布的科学声明:美国神经病学学会确认该声明作为神经科医生继续教育工具的价值

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国际脑血管病杂志 2009年第9期17卷 643-660页

作者： J.Donald easton Jeffrey L.Saver Gregory W.Albers mark J.Alberts Seemant Chaturvedi Edward Feldmann Thomas S.Hatsukami Randall T.Higashida S.Claibome Johnston Chelsea S.Kidwell Helmi L.Lutsep Elaine Miller Ralph L.Sacco 李海峰(译) 高翔(译) 不详青岛大学医学院附属医院神经内科 266003

本科学声明面向为短暂性脑缺血发作(transient ischemic attacks,TIA)患者提供医疗诊治的临床医生和相关医疗卫生人员。采用正规的证据复习方法对1990-2007年7月期间Medline数据库进行系统的文献检索,并运用证据表、汇总分析和病例资料... 详细信息

本科学声明面向为短暂性脑缺血发作(transient ischemic attacks,TIA)患者提供医疗诊治的临床医生和相关医疗卫生人员。采用正规的证据复习方法对1990-2007年7月期间Medline数据库进行系统的文献检索,并运用证据表、汇总分析和病例资料的合并分析,对数据进行综合处理。本文支持以下基于组织学的TIA定义:局灶性脑、脊髓或视网膜缺血引起的短暂性神经功能障碍发作,且无急性脑梗死。TIA患者的近期卒中风险较高,可根据临床量表、血管影像学和磁共振弥散加权成像进行风险分层。诊断推荐包括:TIA患者应在发病24h内接受神经影像学评价,最好是应用包括弥散序列在内的MRI;应进行无创性颈部血管成像检查,最好是无创性颅内血管成像;对于未能确定血管病因的患者,TIA发病后应尽快进行心电图检查,也应考虑持续心电监测和超声心动图检查;应进行常规血液化验;对于发病72h内就诊并且ABCD^(2)评分≥3分(提示近期复发风险较高)或在门诊不能迅速完成诊断评价的TIA患者,应收入院治疗。

关键词：美国心脏协会科学声明脑脑缺血缺血卒中短暂性脑缺血发作急性卒中综合征急性脑血管综合征

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