T1相(Al2CuLi)对铝锂合金各向异性的贡献

在分析T1相基本特性的基础上，结合相关工作，论述T1相与位错的交互作用、T1相与结构的相互影响、T1相对合金各向异性的贡献及稀土Ce的作用。结果表明，T1相因其分布及形貌而难以有效阻碍共面滑移；T1相对形变织构的形成起调整作用；织构的存在使T1相的分布及其与位错的作用发生变化，从而使其强化贡献具有各向异性。Ce影响形变织构的形成和合金的时效析出，并对共面滑移具有双重作用，从而改变T1相强化的各向异性。     

内张钢圈加固盾构隧道的多环有限元模拟研究

内张钢圈作为传统的管片加固方法,用以应对盾构隧道处于不良工况下出现的结构破坏和变形过大等问题。在考虑环间力的作用下,运用MIDAS GTS NX对三环盾构管片进行精细化模拟,从管片的累计横向变形、错台以及构件塑性发展情况等方面衡量内张钢圈的加固效果。研究结果表明,管片的最大变形出现在腰部,加固后管片的累计横向变形可减小50%,管片整体未进入塑性状态;管片的最大错台出现在中环邻接块和标准块的接缝处,加固后最大错台大幅减小;内张钢圈加固法可延缓管片构件进入塑性和破坏状态,且有效降低环间作用力对中环管片的影响。     

Microscopic characterization of semi-solid aluminium alloys

The microstructural evolution and element distribution of the Al-4Cu-Mg alloy during semi-solid compression were investigated,and the precipitate behavior and dislocation morphology were discussed.The experimental results show that the microstructure,the number of CuAl2(θ phase) precipitates,and the dislocation density of the Al-4Cu-Mg alloy depend apparently on the process parameters.More segregation of Cu at the grain boundary happens with an increase of deformation temperature and a decrease of strain ra...     

Effects of strain rate on dislocation for TA15 alloy during hot compressive deformation

The effects of strain rate on the dislocation type and dislocation configure of TA15 alloy were investigated.The experimental results show that the operating dislocation type changes from c type to c and a+ c type with increasing strain rate under the deformation condition of 900℃,60% strain.Under the condition of 900℃,60% strain and 0.001/s strain rate,lots of orientate dislocation cellular configurations and sub-grains,many dislocations pile up before sub boundary.When the strain rate increases to 0.1/s,some dislocations exhibit curved and dislocation tangles and pile-ups can be found,suggesting more dislocations and much stronger interactions among dislocations.     

The effect of hydrogen on the electronic structure of kink in bcc iron

The electronic structures of kinks in the [100](010) and 1/2[111](−110) edge dislocations in bcc iron containing hydrogen are investigated by means of the first-principles DMol method and the discrete variational method. The effects of hydrogen on the kinks are discussed. The results show that hydrogen forms weak bonding states with its neighboring host atoms, and since hydrogen draws charge from its neighboring host atoms, the interactions between most of the host atoms are weakened compared with those of the corresponding atomic pairs in the clean kinks. This indicates that the migration of kink, i.e. the motion of dislocation, is easier in the doping hydrogen kink than in the clean kink, which may be the solid solution softening effect resulting from the impurity hydrogen. Supported by the National Basic Research Program of China (Grant No. 2006CB605102) and Science Foundation of Central South University of Forestry & Technology (Grant No. 06y016)     

(1102)γ面蓝宝石生长的(1120)α面氮化镓研究

自发极化和压电极化是氮化镓制作光电器件没有解决的问题,对非极性GaN材料的研究解决了极化现象.采用低温AIN作为缓冲层,在(1102)γ面蓝宝石和(0001)с面蓝宝石上分别生长了(1120)非极性α面和(0001)极性с面GaN,用原子力显微镜和高分辨X射线衍射、光致发光谱比较了生长在γ面蓝宝石上的α面GaN和с面蓝宝石上的с面GaN,α面GaN材料质量和с面GaN相差较大,在α面GaN上发现了三角坑的表面形貌,这和传统的с面生长的极性GaN截然不同.对α面GaN的缺陷形成原因进行了讨论,并且确定了三角坑缺陷的晶向.     

Dispirations,disclinations, dislocations,and chain twist in polyethylene crystals

It is proposed that the twist in polyethylene chains that can result from crystallization and subsequent deformation aggregates at boundaries and becomes a template for further reorganization that results in the long period observed in polyethylene fibres. The observed lower density at the boundaries requires the transport of free volume to the twist boundaries. Dispirations, disclinations and dislocations are crystallographic defects that are involved in the necessary transport mechanism. Twist and bend, derived from the Eulerian angles which are computed from the sets of chain internal coordinates, relate the orientation of different segments of a chain. Twist and bend are useful for the characterization of both crystallographic defects and arbitrary conformations of polymer chains. Defects, along with folds, chain ends, and ordinary edge and screw dislocations provide a basis for interpretation of structure-property relationships in solid polyethylene.     

30CrMnSiA绝热剪切带显微观察与分析

采用分离式霍普金森装置对30CrMnSiA的片式帽型试样进行动态剪切,利用光学显微、扫描电镜、透射电镜、显微硬度等金相分析方法对材料绝热剪切带的微观结构演化过程进行分析。研究发现,随着加载应变率的增大,剪切带发生由形变带到转变带的变化趋势,转变带呈"白亮"色,带内由尺寸约为50 nm的低位错、等轴晶粒组成,这是典型的再结晶晶粒特征。转变带形成过程可分为剪切变形、晶粒细化、晶粒断裂旋转、动态再结晶4个阶段。     

蓝宝石衬底上侧向外延GaN中的位错降低

采用侧向外延(ELOG)方法,在制作了条形掩膜图形的GaN衬底上用MOCVD生长高质量GaN.AFM,化学湿法腐蚀及TEM分析表明:采用两步法ELOG生长的GaN中,掩膜下方的缺陷被掩膜所阻挡,窗口区内二次生长的GaN的位错也大幅降低;在相邻生长前沿所形成的合并界面处形成晶界;化学湿法腐蚀无法得到关于合并界面处缺陷的信息.侧翼区域中极低的穿透位错使得ELOG GaN适用于在其上制作高性能的氮化物基激光器.     

福建省漳平电厂发电机护环开裂的研究

就基体材料的组织特征以及是否由于基体材料本身问题导致护环开裂进行研究。利用金相显微镜和电子显微镜对福建省漳平电厂发电机护环的金相样品进行观察与分析 ,发现护环材料运行一定时间后 ,奥氏体基体组织中出现滑移带。在电镜下可观察到位错缠结和位错胞 ,并伴有少量马氏体和形变孪晶。研究表明 :该基体材料的组织特征属于正常运行的组织转变 ,不会产生裂纹等异常现象。