材料期刊网

Microstructural Stability of a Single Crystal Superalloy DD8 during Thermal Exposure

K.Y.Cheng , D.H.Kim , Y.S.Yoo , C.Y.Jo , T.Jin , Z.Q.Hu

材料科学技术（英文）

Microstructural stability of a nickel base single crystal alloy DD8 has been investigated. Standard heat treated specimen showed good microstructural stability at 950℃. While under the as-cast condition, a kind of rod-like phase precipitated in the interdendritic region of as-cast specimen during thermal exposure. The phase, which has bcc structure, was enriched with Cr. Thermo-calc also predicted precipitation of a bcc phase at around 950℃. The Cr-rich bcc phase was considered as α-Cr and formed due to the segregation of Cr under the as-cast condition.

关键词: DD-8 , null , null , null

SIMULATON ON WELDING PROCESS OF T - JOINTS

H. Y. Zhao , A. L. Lu , Q. Y. Shi and F. Yan (Welding Division , Department of Mechanical Engineering , Tsinghua University , Beijing 100084 , China)

金属学报(英文版)

T-joints are widely used in ship manufacturing and other welding structures.The welding residual stress and deformation hare significant influence on failure and service life in welding structures.By us- ing of 3D thermal elasto - plastic FEM, the temperature fields,stress fields and deformation of weld- ing processes on T - joints are analyzed in this paper.The moving heat source is considered in the com- putation. Moreover, weld metal filling and multiple - pass welding are simulated using activate/deac- tivate ability.For avoiding "locking" in full integration elements of welding computation,the re- duced intergration elements are used in weld area.The nonlinear FEM analysis program MARC is used to complete the computations, as well as its user subroutines that are programmed to develop the special techniques needed in the simulation of welding process.Some different welding procedures are com- pared, and the welding residual stress and deformation are discussed in details.

关键词: welding , null , null , null , null

Magnetic properties of 1T-TaS2

Chinese Physics Letters

The magnetic properties of 1 T-TaS2 and 1 T-Fe-0.07 Ta-0.93 S-2 have been studied, Experimental results show that the phase transition temperature of 1 T-TaS2 is a function of the magnetic field, At low temperatures, both compounds are in a mixed state of charge density wave -spin density wave due to the coherent superposition of antiferromagnetic coupling.

关键词: density

T300和T700炭纤维的结构与性能

李东风 , 王浩静 , 贺福 , 王心葵

新型炭材料 doi:10.3969/j.issn.1007-8827.2007.01.011

利用SEM、元素分析、XRD和激光Raman光谱研究了T300和T700的形貌、化学组成和微观结构参数.结果发现:T700炭纤维表面光滑,而T300炭纤维的表面有大量的沟槽.表明前者是用干喷湿纺原丝,后者是用湿法纺丝原丝.两种纤维的断面均呈现出颗粒状特征.T700的含碳量高于T300,含氮量低于T300.两者的微观结构参数(d002、La和Lc)差异佐证了T700的炭化温度高于T300.T700的择优取向角Z比T300小2.3°,是石墨微晶致密有序排列的反映,因而使其体密度比T300高2.27%,空隙率低7.54%.所以致密化赋予了T700较高的拉伸强度.

关键词: PAN基炭纤维 , 微观结构 , XRD , Raman光谱

Effects of Mn and Cu doping in La(T,Al)(13) (T=Fe,Co) on crystal structure and magnetic properties

Journal of Alloys and Compounds

The crystal structures and magnetic properties of Mn and Cu-doped in La(T,Al)(13) (T=Fe,Co) compounds have been investigated by means of X-ray powder diffraction and magnetic measurement. The results show that Mn doping stabilizes the cubic NBZn13 type structure, but both the magnetic moments and the Curie temperature decrease. Cu doping decreases the homogeneity region of the cubic NaZn13 type structure. (C) 1997 Elsevier Science S.A.

关键词: ternary La aluminides;Fe rich rare earth intermetallics;magnetic;properties;intermetallic compounds;rare-earth;transition;nd

S-T-B流型判别方法

孙长征 , 宇波 , 魏进家

工程热物理学报

通过分析气相、液相、管壁之间的关系,将气液混输管道中的流型划分为五种,并总结了各流型的特点及气液相和管壁间的几何关系;在对Baker、Brill、Beggs-Brill、Taitel、段塞特征分析(SCA)等流型判别方法进行分析的基础上,提出了一种综合使用SCA、Taitel和Brill三种方法的流型判别方法 S-T-B法.经算例验证,该方法对气液两相混输的流型判断准确性较高,可以作为气液混输工艺计算过程中确定流型的方法.

关键词: 气液混输 , 流型 , 段塞特征分析法 , S-T-B

6061-T4铝合金搅拌摩擦焊T型接头缺陷及性能

周光 , 杨新岐 , 徐效东 , 张照华

航空材料学报 doi:10.3969/j.issn.1005-5053.2012.4.005

对板厚3mm的6061-T4铝合金T型接头进行搅拌摩擦焊接研究并具体讨论了旋转速率(ω)及焊接速率(ν)对焊接缺陷及力学性能的影响.结果表明:对给定的夹具形式和搅拌工具,当ν不变时焊缝前进侧筋板圆角过渡处容易产生随ω/ν增大而减小的隧道缺陷,后退侧圆角区易出现清晰的“Z”连接线；壁板出现两个随ω增大而扩大的软化区域,而壁板焊缝中心的硬度随ω增大而升高；T型接头筋板焊缝热力影响区同样被软化,其硬度较母材降低17.0％；局部组织软件是造成所有接头沿壁板方向加载抗拉强度下降的重要原因,其最高抗拉强度只达到母材的73.8％,隧道缺陷是引起ω=1008r/min筋板方向强度降低的主要原因,而ω=1541r/min和ω=2256r/min筋板方向强度降低主要归结于T型接头中热力影响区组织的软化,其中当ω/ν=1541/218 r/mm时,沿T接筋板方向抗拉强度最高可达到母材的83.5％.

关键词: 搅拌摩擦焊 , T型接头 , 焊接缺陷 , 力学性能

2A70-T6铝合金T型接头搅拌摩擦焊工艺研究

何志宏 , 李宝华 , 唐众民 , 鄢江武

兵器材料科学与工程 doi:33-1331/TJ.20110905.2223.006

采用3种规格的搅拌头进行2A70-T6铝合金T型接头搅拌摩擦焊试验,并对焊缝横截面进行观察以及焊缝抗拉强度的测试.结果表明:焊缝中前进侧过渡区的金属变化急剧,拉长的晶粒成流线状分布,返回侧过渡区的金属变化缓和,由焊核区细小晶粒缓慢过渡至母材较大的晶粒;随着搅拌针根部直径的增加,焊核的宽度也增大;为了获得无缺陷的接头,焊接速度增大时,顶锻压力必须协同增大,随着顶锻压力的增大,焊缝的抗拉强度也增大.

关键词: 2A70-T6 , 铝合金 , T型接头 , 搅拌摩擦焊

Thermal shifts and electron-phonon interactions of T-4(2) and T-4(1). broad bands for ruby

Communications in Theoretical Physics

For the first time, by taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d(3) electronic configuration, the values of parameters in expressions of Raman and optical-branch terms of thermal shifts (TS) due to EPI for three levels, T-4(2) band and T-4(1) band of ruby have been evaluated; the contributions to TS of T-4(2) and T-4(1) broad bands from thermal expansion have also been. calculated; and then, the TS of the peak energies of 'T2 and 4 Ti broad bands have been calculated. The results are in satisfactory agreement with observed data. The values of single-electron reduced matrix elements representing the strengths of EPI of T-4(2) and T-4(1) bands have respectively been determined. For TS of the peak energies of T-4(2) and T-4(1) bands, it is found that the contribution to TS from the second-order term in EPI Hamiltonian is dominant; TS due to EPI of acoustic branches are over two times as much as those of optical branches, and both of them increase rapidly with temperature; the neighbor-level term is insignificant; the contribution to TS from thermal expansion is specially important, and all the three terms of TS of T-4(2) or T-4(1) band axe red shifts.

关键词: crystal fields;optical spectral bands;electron-phonon interaction;thermal expansion;thermal shift;theoretical calculations;high-pressure;field;spectroscopy;spectra

T型接头搅拌摩擦焊接的研究进展?

刘德佳 , 丁江灏 , 涂文兵 , 赵龙志 , 林凤涛

材料导报 doi:10.11896/j.issn.1005-023X.2016.23.010

T型接头是满足轻量化需求的关键结构之一，但传统熔化焊在T型构件焊接方面并无优势。作为一种固相焊接技术，搅拌摩擦焊采用特殊的焊接夹具，对中、薄板T型构件实行单面焊三面成型技术，显著降低焊接热输入、减少焊接变形，因此 T 型接头搅拌摩擦焊可能是一种极具发展前景的工艺方法。从搅拌摩擦焊接 T 型接头(FSW-T)的焊接工艺、焊接缺陷、显微硬度、力学性能与数值模拟方面概述了国内外研究现状，揭示了 FSW-T焊接领域尚需解决的关键科学问题，对该领域未来的研究方向提出了展望。

关键词: 搅拌摩擦焊 , T型接头 , 工艺参数 , 焊接缺陷 , 力学性能