10月24日（周五）名师讲坛：金属复合材料及特性
北京交通大学“与大师面对面”名师讲坛系列活动
（机电学院，2014年秋季第5周）
（报告一）
【主 题】：Al/Al-Cu-Fe metal matrix composites （Al/Al-Cu-Fe 金属基复合材料）
【主讲人】：Joel Bonnevile 教授，法国普瓦捷大学物理系主任
【时 间】：2014年10月24日（星期五）上午10：10-12：00
【地 点】：机电学院大会议室（机械工程楼Z802B）
【主 办】：研究生工作部
【承 办】：机电学院
【主讲人简介】：
Professor Joel Bonnevile is the head of the department of Physics of Poitiers University since 2011. His main research activities are: (1) Physical metallurgy, characterization of structure/mechanical property relationships in a variety of pure metals, composite materials, intermetallic and complex alloys; (2) mechanical properties of thin films; (3) modeling of dislocation core structures and of fundamental dislocation mechanism.
He has published 125 articles in scientific journals and contributed 3 chapters in books. He is a referee for different journals: Journal of Applied Physics, Journal of Alloys and Compounds, Physical Review B, Materials Science and Engineering A, etc.
Joel Bonnevile教授自2011年起担任普瓦捷大学物理系主任，其主要研究领域包括：（1）物理冶金学、金属结构/力学性能的表征、复合材料、金属间化合物及复杂合金；（2）薄膜材料的机械性能；（3）位错核心结构与基本位错机制的建模。
他已发表了125篇论文并与人合作撰写了3本书的相关章节。同时，他担任很多科学期刊的审稿人，如：应用物理杂志，合金和化合物，物理评论（B），材料科学与工程（A）等。
【讲座简介】：
In this talk, the mechanical properties of icosahedral quasicrystalline (i-QC) Al-Cu-Fe alloys make them very attractive as reinforcement particles for metallic matrix composites (MMC). Al-base composites reinforced by i-QC Al- Cu-Fe particles have been synthesised since nearly two decades, but their mechanical properties are still poorly known. In this work, Al/Al-Cu-Fe MMCs were produced at two temperatures, i.e. T = 673K and T = 873K, by hot isostatic pressing. Crystallographic and chemical composition investigations were performed on the as-synthesised MMCs for identifying the resulting phases. At T = 673K, the reinforcement particles are still of the original i-QC phase, whereas at T = 873K a phase transformation occurs for the reinforcement particles, which have the ω-Al-Cu-Fe tetragonal crystalline structure. Compression tests were performed on the two composites at constant strain-rate in the temperature range 293K - 773K. The flow stress of both composites is strongly temperature dependent, suggesting that thermally activated processes control plastic flow. The s0.2% stress of two composite materials also exhibits two temperature regimes with a common transition temperature at approximately 550K. In the low temperature regime, s0.2% differs for the two composites both in value and temperature dependence, while in the high temperature regime s0.2% has similarly values. Transmission electron microscopy observations suggest that micro- and nano-particles play different roles in the strengthening of the two composites.
本次讲座的主要内容是关于金属基复合材料的增强颗粒二十面体准晶铝-铜-铁合金的一些研究。由于铝-铜-铁合金（I-QC）具有优良的力学性能，引起了人们广泛关注。近二十年来，I-QC颗粒增强的铝基复合材料已被合成，但对其机械性能的研究甚少。Joel Bonnevile教授等人利用热等静压的方法在两个温度下(T=673K，T=873K)制备了Al/Al - Cu - Fe金属基复合材料，同时对制备的金属基复合材料的晶体结构及化学成分进行了分析，具体结果如下：
（1）I-QC增强相在T =673K时依然保持原有形态，当T=873K时，发生相变，生成ω-Al-Cu-Fe正方晶体结构。
（2）在恒定应变速率、温度范围为293K - 773K的条件下对制备的两种复合材料进行了压缩实验。结果表明，温度对复合材料的屈服应力有很大影响，表明热激活过程控制塑性流动。
（3）两种复合材料的屈服应力s0.2% 呈现出两个温度区间，其转变温度在550K左右。在低温区间，两种复合材料的s0.2%值及其对温度的依赖性是不同的，而在高温区间，两种复合材料具有相近的s0.2%值。
（4）TEM观察发现，微米颗粒和纳米颗粒对增强复合材料所起的作用不同。
（报告二）
【主 题】：Electronic structure and transport properties of Ti2Al(CxNy) MAX phase solid solution （Ti2Al(CxNy) MAX相固溶体的电子结构及输运特性）
【主讲人】：Sylvain Dubois 教授，法国普瓦捷大学主管科研副校长
【时 间】：2014年10月24日（星期五）下午14：00-16：00
【地 点】：机电学院大会议室（机械工程楼Z802B）
【主 办】：研究生工作部
【承 办】：机电学院
【主讲人简介】：
Professor Sylvain Dubois is the Chief of the departement of Chemistry of the Poitiers Institute of Technology. He is the vice-president of the
He has published 70+ articles in scientific ISI journals, hindex=18 and 118 communications in congress among which 57 oral communications as speaker. He contributed 2 chapters in books, was an organizer of 3 symposiums on MAX phases (Pittsburgh, Daytona Beach and Houston (USA)), is a referee for different journals: Journal of Applied Physics, Journal of the American Ceramic Society, Journal of Alloys and Compounds, Physical Review B, etc.
His main research activities are: synthesis and properties of nano-materials; MAX phases-nanolaminated materials and related properties; relationship between micro or nano-structure and physical properties; studied materials: Magnetic nanowires, superconducting nanowires, multilayered nanowires-Relation between the reduced dimension of the object under study and the scaling length of the physical property – such a project led him to work during 4 years with Pr. A. Fert (Nobel Prize in physics in 2007).
Sylvain Dubois教授是普瓦捷技术研究院化学系主任，自2012年起担任普瓦捷大学副校长，主管科研。他发表论文70多篇，其中高引用次数论文18篇，参加会议118次，其中口头报告57次。与人合作撰写书籍两章，是3个国际会议（匹兹堡，美国代托纳比奇和休斯敦国际会议）中关于MAX相分会的组织者，担任多个期刊的审稿人，例如：应用物理杂志，美国陶瓷学会杂志，合金的和化合物杂志，物理评论B等。
他的主要研究领域包括：纳米材料的合成和性能；MAX相-纳米层状材料材料及相关性能;微型或纳米结构和物理性能之间的关系;研究的材料：磁性纳米线，超导纳米线，多层纳米线在减小尺寸和物理特性的缩放长度之间的关系--这个项目使他有机会与 A.
【讲座简介】：
Ti2AlCxNy solid solutions are synthesized by using Hot Isostatic Pressing. The X site solid solution effects are investigated by focusing on the electronic structure and transport properties of the Ti2AlCxNy MAX phases. Combining electron energy-loss spectroscopy (EELS) and band structure calculations, it is demonstrated that solid solution effects induce weak perturbations on the electronic structure. Solid solution effect thus mainly results in a rigid shift of the Fermi energy in a flat part of the electron density of states of Ti2AlC (or Ti2AlN). From these observations, the variations of two key parameters of the conductivity are rationalized. The relative variations of the residual resistivity in the whole composition range are shown to be rather small which well agrees with the weak disorder evidenced from EELS. However, the values of the slope of the resistivity versus temperature variation are shown to vary quite significantly, evidencing a deviation from Matthiessen’s rule in these systems. By comparing the experimental data with calculations based on the semi-classical Boltzmann equation, it is demonstrated that the observed variations are due to a combination of band structure effects and changes in the scattering mechanisms.
本研究采用热等静压法合成Ti2AlCxNy固溶体。通过研究Ti2AlCxNy材料的电子结构和输运特性来研究MAX相中X位置固溶效应。通过电子能量损失谱（EELS）和能带结构的计算证明固溶体效应引起了电子结构的微弱扰动。固溶体的影响主要是由此导致Ti2AlC（或Ti2AlN）的电子密度状态的平坦部分，费米能级发生刚性转变。这些观察表明电导率的两个关键参数的变化是合理的。在整个组合物范围内的残余电阻相对变化是相当小的，这与用EELS证实的弱紊乱一致。然而，电阻率随温度变化的斜率值变化显著，与体系中的马修森规则有偏差。通过对比实验数据与基于半经典波尔兹曼方程的计算表明，所观察到的变化是由于能带结构的影响和散射机制的变化共同作用引起的。