佟媛媛
,
华勤
上海金属
doi:10.3969/j.issn.1001-7208.2010.03.011
运用热分析技术研究了冷却曲线特征值与319铝合金中化学成分之间的关系,并进行回归分析.结果表明,在不考虑工艺因素的情况下,试样的硅含量与α-Al枝晶生长回升温度TαDENG之间的相关性最大,相关系数r为-0.65,以硅含量可预测α-Al枝晶生长回升温度.在浇注过程中,冷却速度与α-Al枝晶生长回升温度TαDENG密切相关,相关系数为r=-0.72.在相同的冷却条件下,铝合金的浇注温度和浇注量对冷却速度有明显的影响,因此,可以通过调整浇注温度和浇注量,控制铝合金的冷却速度,进而也可预测铝合金中α-Al枝晶生长回升温度TαDENG.
关键词:
319铝合金
,
热分析
,
特征值
,
浇注工艺
MAO Weimin University of Science and Technology
,
Beijing
,
100083
,
China.
材料科学技术（英文）
The recrystallization texture in commercially pure Al is investigated after the samples are rolled differently and annealed.The samples with low rol- ling reductions could be generally recovered or recrystallized in situ and characterized by the re- tained G{110}<001>component.This recovery process decreases during annealing with the increase of reduction.The appearance of the B/R{359}. <132>and R{123}<634>components de- pending on the rolling reduction is investigated and the less developed Cube{100}<001>component in commercially pure ahninium is also discussed.
关键词:
recrystallization
,
null
,
null
,
null
Ruwei GAO
,
Wei CHEN
,
Jiancheng ZHANG
,
Weicun FONG
,
Wei LI
,
Xiumei LI
材料科学技术（英文）
For both sintered and nanocomposite NdFeB magnets, deltaM(H) of the Henkel plot increases from zero, and reaches a peak, then decreases and changes to the negative values with increasing applied field. This shows that the intergrain interaction changes from the exchange-coup ling type into the magnetostatic interaction type. The magnetic field corresponding to the peak of deltaM(H) is slightly smaller than the coercivity of magnet. The peak of deltaM(H) for aligned sintered magnet is greater than that for misaligned magnet. deltaM(H) peak of the nanocomposite NdFeB magnets increases with decreasing grain sizes. It indicates that the effect of alignment field on the properties of magnet is similar to that of exchange-coupling interaction.
关键词:
TAO Zengyi LUO Jiaming Huazhong University of Science and Technology
,
Wuhan
,
China TAO Zengyi
,
Faculty of Metallic Materials
,
Dept.of Mechanical Engineering No.2
,
Huazhong University of Science and Technology
,
Wuhan 430074
,
China
金属学报(英文版)
The influence of laser surface melting and induction hardening on the surface structure,con- tact fatigue life and failure behaviour of the nodular cast iron has been investigated.The con- tact fatigue life can be improved by both laser treatment and induction hardening,but the fail- ure process and type are different from each other.The former is due to lumpy and deep spal- ling caused by crack propagation between the quenching zone and the substrate,and the latter is due to nubby and surface flaking caused by the oil wedged action into surface cracks.
关键词:
surface hardening
,
null
,
null
,
null
Journal of Applied Physics
Motivated by the recent experimental fabrication of half-metallic MnSb and CrSb thin films with metastable zinc-blende structure [Aldous et al. Phys. Rev. B 85, 060403(R) (2012); Deng et al. J. Appl. Phys. 99, 093902 (2006)], we investigate the structural, electronic, and magnetic properties of TiSb in both ground-state NiAs and metastable zinc-blende phases by using the first-principles calculations. It is shown that the ground-state NiAs phase is metallic and nonmagnetic, but the metastable zinc-blende phase exhibits half-metallic ferromagnetism with a magnetic moment of 1.00 mu(B) per formula unit. We also reveal that the half-metallicity in bulk ZB TiSb is lost at the Sb-terminated (001) surface due to the appearance of surface states within the gap of the minority-spin channel, but the Ti-terminated (001) surface retains the bulk half-metallicity, which makes ZB TiSb a promising candidate for the possible epitaxial growth of half-metallic thin films or multilayers on semiconductor substrates for spintronic applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739744]
关键词:
room-temperature ferromagnetism;molecular-beam epitaxy;crsb;cras;spintronics;state;mnas
刘云川
,
李志华
,
李爱明
材料导报
在EB-PVD/(NiPt)Al涂层中存在皱曲(Rumpling)现象 ,导致涂层的早期失效.综述了皱曲(Rump-ling)力学模型的研究进展,主要包括3个方面的问题:皱曲的力学模型、数值计算方法研究现状;皱曲的机理及力学模型研究中存在的问题和不足;进一步研究皱曲机理并改进模型的途径.提出了在粘结层晶体尺度内棘轮效应与热扩散间存在耦合作用的设想,并认为这种耦合作用是形成皱曲的根本原因.
关键词:
热障涂层
,
皱曲
,
力学模型
,
棘轮效应
,
循环塑性
LIU Shan LU Deyang HUANG Tao ZHOU Yaohe National Lab of Solidification Processing
,
Northwestern Polytechnical University
,
Xi'an
,
China LIU Shan
,
lecturer
,
National Laboratory of Solidification Processing
,
Northwestern Polytechnical University
,
Xi'an 710072
,
China
金属学报(英文版)
An experimental apparatus,which has a convection generator and an aid-heater,is developed for the study of the effect of stable laminar liquid flow on the directional solidification process by the use of transparent alloy SCN-2wt-% Ace.The flow is perpendicular to primary arms. By in-situ observation and photographing at different specific moments,it has been found that such a flow can cause a great change in primary spacings of constrained columnar crystals:for cells,the spacings become smaller;but for dendrites,they become larger.The former is mainly due to the tilted growth of upstreamside branches,while the latter is mainly due to the coup- ling effect of liquid flow with solutal field around dendrite tips.The faster the liquid flows,the further smaller the cell spacing and the further larger the dendrite spacing.
关键词:
forced liquid flow
,
null
,
null
,
null
Z Zhang
,
ZH Tu
,
L.F. Li
,
L.Z. Zhaoand D. Jin (Cryogenic Laboratory Chinese Acaderw of Sciences
,
Beijing 100080
,
China )H.J Lu (Beijing Institute of Aerospace Materials and Technology
,
Beijing 100076
,
China)
金属学报(英文版)
Low temperature may greatly affect the mechanical properties of materials. Some in-teresting mechanical phenomena were detected at very low temperature. In this study,a multi-sample tensile installation was designed to study the plastic deformation be-havior for Ti-5Al-2.5Sn extra-low-interstitial (ELI) alloy at liquid helium temperature.The special geometrical instability phenomena in low temperature, serrated deforma-tion and multi necking, was studied in detail in this project. Slip and twinning were determined in the process of plastic fiow by SEM/TEM analysis. Efficts of temper-ature and sequential straining on load drops in tensile stress-strain curves were also studied. Optical measurement method was used to gauge the geometrical characteristic of multi-necking specimens. The sensitivity of partial thermoplastic deformation and the equivalency of low tempemture with high velocity of this material were studied by using micro-mechanics analysis.The criterion of geometrical instability has been discussed. A computer simulation of the low temperature instability of plastic fiow in Ti-5Al-2.5Sn ELI alloy has been carried out. A computer model has been established which links the hot dtffusion and the plastic fiow of hcp alloys under assumption that the tempemture is homogeneous within the specimen and that the heat exchange with the thermal bath is the control-ling step in the heat release. The computer simulation of the deformation curves as a function of several mechanincal, geometrical and thermal parameters provides a re-alistic description of the experiments. The experimental data available are discnssed in the light of the computer simulation model.
关键词:
mechanical property
,
null
,
null
