原位TiB2颗粒增强铝基复合材料及其力学性能

对原位反应合成TiB2／A356铝基复合材料微观组织和力学拉伸性能进行了研究。结果表明，原位反应生成的颗粒增强相在复合材料基体中分布均匀，基体与颗粒间的界面洁净。复合材料强度随着颗粒含量的增加显著提高，与基体合金相比，TiB2质量分数为8％的TiB2／A356复合材料强度和弹性模量的提高幅度约为28％，TiB2质量分数为16％的TiB2／A356复合材料强度和弹性模量的提高幅度约为35％。复合材料的断裂主要是由于基体与颗粒界面脱粘，在拉伸应力作用下由此萌生微裂纹并扩展，导致界面处的基体撕裂，从而降低复合材料塑性。     

高纯均匀A1-V4中间合金制备工艺研究

利用铝热还原法，通过过量铝粉一步还原工业V2O5得到Al－V50合金。在300kg熔铝用中频感应炉中， 温度1050－1150℃，把Al－V50分批加入Al99．85熔体，机械装置强力搅拌条件下。可以生产出优质高纯且成分均匀的Al－V4中间合金，并用于生产各种大型复杂关键的ZL205A合金铸件。     

铜钛合金调幅分解之特征

通过透射电子显微分析和Ｘ射线衍射分析对Ｃｕ－５２Ｔｉ（％，原子分数，下同）合金的调幅分解过程进行了研究。确认调幅分解是Ｃｕ－Ｔｉ合金相变初期的过程之一。盐水淬冷不能抑制调幅分解，淬火态调幅波长约为５７ｎｍ。研究表明，调幅分解与调幅组织的长大是两个完全不同的过程，分别属于连续相变和非连续相变。这两个过程的波长长大动力学均符合λ３－λ３０＝ｋｔ定律，长大激活能分别为１７６ｋＪ／ｍｏｌ和１３４ｋＪ／ｍｏｌ。电镜下看到的调幅组织不能作为调幅分解发生的判据。     

Oxidation Mechanism of Ni—20Cr Foils and Its Relation to the Oxide-Scale Microstructure

The oxidation behavior of Ni—20Cr foils of 100- and 200-m thickness wasstudied in air between 500 and 900°C. Simultaneously, the morphology,microstructure, and composition of the oxide layers were determined byscanning and transmission electron microscopies. Depending on thetemperature, the oxide layer differed significantly. The scale formedat all temperatures was complex, with an outer NiO layer having columnargrains, and an inner layer of equiaxedNiCr₂O₄+NiO+Cr₂O₃ grains. At low temperatures (500 and 600°C),the chromium content was insufficient to form a continuousCr₂O₃ layer, while such a continuous layer formed at theinner interface at oxidation temperatures of 700 to 900°C. At 600°C,internal oxidation of chromium occurred in the substrate. The oxidationmechanism is described taking into account these morphologies and theoxidation kinetics. The observation of no significant differences betweenthe oxidation behavior of thin strips and thick materials is related to thelimited exposure times of the study.     

铝电解用TiB_2阴极涂层固化、炭化的升温制度

采用DTG ,DDTA等热分析手段 ,研究了高温固化、炭化过程中 ,铝电解用TiB2 阴极涂层糊料的质量和能量的变化速率 ,制定了涂层的变速固化、炭化升温制度 ;在此基础上 ,研究了升温制度对TiB2 阴极涂层性能的影响。结果表明 :变速升温制度优于匀速升温制度 ,采用变速固化、炭化升温制度所制备的涂层形变小、无裂纹 ,其抗拉强度达 3.13MPa,电阻率为 2 3.2 μΩ·m ;而采用升温速度为 10 .3℃ /h的匀速固化、炭化升温制度制备的涂层形变大、裂纹多 ,抗拉强度小 (2 .6 9MPa) ,电阻率大 (2 8.6 μΩ·m)。     

分子动力学模拟铜纳米团簇的结构稳定性

利用分子动力学研究了原子数为13～1 055的铜纳米团簇.结果表明:随着尺寸的减小,铜纳米团簇的结构发生晶体→非晶→晶体→非晶→晶体→非晶的转变.团簇平均原子结合能随着尺寸的减小而减小,且只依赖于短程有序,这说明了团簇平均原子结合能一般不能够作为非晶与密堆结构晶体转变的判据.平均原子间距不但依赖于团簇的尺寸,且对团簇结构的变化敏感,可以作为非晶与密堆结构晶体转变的一个判据.对偶分布函数的研究表明,大尺寸团簇的内部和表层原子结构都表现出晶格收缩效应,且不同于相应块体晶格,这表明了目前文献中关于团簇的块体加表面模型与壳核模型都有待改进.     

(ZrAl3+ZrB2)/Al复合材料的制备和微观组织结构

采用混合盐反应法,以KBF4和K2ZrF6粉剂为原料在铝熔融体中制备了(ZrAl3 ZrB2)/Al复合材料.借助于X射线衍射仪、电子探针和透射电镜对复合材料的物像和增强相进行了观察,结果表明ZrB2颗粒呈等轴或等轴颗粒状,为六方结构,尺寸大部分小于1μm,ZrAl3相大部分呈长条状,两种增强相整体分布较为均匀,且与Al的界面光滑洁净,没有其它界面生成物.对复合材料的硬度做了测试,原位合成增强相的引入显著提高了复合材料的HRB硬度.     

掺杂石墨/Cu钎焊接头残余应力的分布特征及中间层的作用

利用有限元方法,模拟分析了掺杂石墨/Cu钎焊接头残余应力的分布特征。分析结果表明,对接头有害的较大残余应力分布在石墨棱角距离焊缝约0.8mm处的狭小区域;降低连接温度、减少连接时间及增加钎焊压力均有利于减小接头残余应力,优化接头的界面应力状态;中间层的加入在一定程度上缓和了接头的残余应力。从缓和效果来看,Cu比Mo作中间层好,而Cu/Mo复合中间层的缓和效果最好,是较理想的中间层材料。     

Nanoscale Studies of the Early Stages of Oxidation of a TiAl-Base Alloy

The strategy to perform nanoscale studies of the initial stages of oxidation of TiAl involved first gaining some information on the electronic structure of pure TiO₂ surfaces and then on TiAl surfaces before and after oxidation both in low- and high-oxygen potentials. Both materials were studied in atomically-cleaned states generated by repeated sputtering and heating. It was found that the oxygen vacancies created additional defect states in the band gap of stoichiometric TiO₂. The results obtained on TiO₂ were used as fingerprints to study the oxide nucleation. The results on the initial stages of oxidation of TiAl confirm the nucleation of Ti₂O₃ islands of nanometer size and monolayer height in a low-oxygen-pressure environment, whilst a TiO₂ layer developed in an atmospheric environment. The ledges on atomically-cleaned surfaces usually acted as nucleation sites.     

Simulation on function mechanism of T1(Al_2CuLi) precipitate in localized corrosion of Al-Cu-Li alloys

1Introduction Al-Li alloys,compared with traditional Al alloys,possess more excellent properties,such as lower density,greater elastic modulus and higher specific strength.In the near future,they would be widely applied in airplane structures.However,they…