Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
材料科学技术（英文）
The effect of interstitial hydrogen on the cohesion of the Al Sigma=11(113) grain boundary (GB) is investigated based on the thermodynamic model of Rice-Wang using the first-principles density function calculation. The results indicate that interstitial H behaves as an embrittler from "strengthening energy" analysis. The reduced GB cohesion due to the presence of H at the GB is attributed to the low affinity between H and Al, and the weakened bonding of Al atomic pairs perpendicular to GB plane.
关键词:
hydrogen;grain boundary;Al-Mg alloys;pseudopotentials;1st-principles
Xiaoguang LIU
,
Xiaowei WANG
材料科学技术（英文）
The effect of interstitial hydrogen on the cohesion of the Al ∑=11(113) grain boundary (GB) is investigated based on the thermodynamic model of Rice-Wang using the first-principles density function calculation. The results indicate that interstitial H behaves as an embrittler from "strengthening energy" analysis. The reduced GB cohesion due to the presence of H at the GB is attributed to the low affinity between H and Al, and the weakened bonding of Al atomic pairs perpendicular to GB plane.
关键词:
Hydrogen
,
null
,
null
Physical Review B
By use of the linear-combination-of-atomic-orbital (LCAO) method for a cluster model, we studied the electronic structure of gamma-from Sigma 11 [1 (1) over bar0](11 (3) over bar) grain boundary doping with N and Mn atoms. The effect of the segregation on the cohesion of the grain boundary is investigated based on the Rice-Wang thermodynamic model. It is found that N could not only largely enhance the cohesion of the grain boundary but also eliminate the detrimental effect of Mn. The cosegregation effect of Mn and N on the cohesion of the grain boundary depends on where they segregate. Nitrogen could be reliably used in alloyed steels as an efficient strengthening element.
关键词:
electronic-structure;phosphorus segregation;stainless-steel;embrittlement;austenite;nitrogen;boron;impurities;fracture;metals
Journal of Physics and Chemistry of Solids
The layered ternary ceramics Ti3SiC2 and Ti3AlC2 are isostructural and can form Ti3Si1-xAlxC2 solid solutions combining the advanced properties of both compounds [H.B. Zhang, Y.C. Zhou, Y.W. Bao, M.S. Li, Improving the oxidation resistance of Ti3SiC2 by forming a Ti3Si0.90Al0.1C2 solid solution, Acta Mater. 52 (2004) 3631-3637; E.D. Wu, J.Y. Wang, H.B. Zhang, Y.C. Zhou, K. Sun, Y.J. Xue, Neutron diffraction studies of Ti3Si0.9Al0.1C2 compound, Mater. Lett. 59 (2005) 2715-2719; J.Y. Wang, Y.C. Zhou, First-principles study of equilibrium properties and electronic structure of Ti3Si0.75Al0.25C2 solid solution, J. Phys.: Condens. Matter 15 (2003) 5959-5968; Y.C. Zhou, J.X. Chen, J.Y. Wang, Strengthening of Ti3AlC2 by incorporation of Si to form Ti3Al1-xSixC2 solid solutions, Acta. Mater. 54 (2006) 1317-1322]. In the present work, the solid solutions of Ti3Si1-xAlxC2 (x = 0, 0.25, 0.33, 0.5, 0.67, 0.75, 1) are investigated by first-principle calculations based on pseudo-potential plan-wave method within the density functional theory framework. The results show that as Al content increases in the solid solution, all the bonds have weakened to certain extents, which lead to an unstable structure both energetically and geometrically. The calculated results are compared and discussed with the reported data for the Ti3Si1-xAlxC2 solid solutions. (c) 2007 Elsevier Ltd. All rights reserved.
关键词:
ceramics;ab initio calculations;electronic structure;electrical;conductivity;oxidation behavior;mechanical-properties;ti3sic2;temperature;ti3alc2;air;si
邹俭鹏
,
阮建明
,
黄伯云
,
周忠诚
材料研究学报
doi:10.3321/j.issn:1005-3093.2005.03.007
制备了HA(ZrO2)/316L不锈钢纤维对称功能梯度材料(FGM),316L不锈钢纤维的含量(体积分数)按20%→10%→0→10%→20%呈轴向对称梯度变化.分析了材料的微观结构和微区元素含量,研究了材料的性能与316L不锈钢纤维含量的关系.结果表明,在HA(ZrO2)/316L不锈钢纤维对称FGM中,316L不锈钢纤维在微观上呈无序和均匀分布状态,它被包裹于HA(ZrO2)基体中,两者紧密结合.316L不锈钢纤维与HA(ZrO2)基体间的界面表现为部分凹凸不平,紧紧地咬合在一起.在FGM基体中发生了微量的韧化相Fe元素扩散,在韧化相316L不锈钢纤维不发生基体相Ca、P元素的扩散,基体与韧化相之间不发生化学反应.随着316L不锈钢纤维含量的增加,HA(ZrO2)/316L不锈钢纤维复合材料的断裂韧性和弹性模量逐渐增加,体现了FGM中各梯度层的力学性能缓和设计.按Miao模型计算HA(ZrO2)/316L不锈钢纤维FGM中的残余热应力为515 MPa,FGM的增韧机理主要为纤维的拔出增韧和层间的裂纹偏转增韧.
关键词:
复合材料
,
功能梯度材料
,
生物材料
,
羟基磷灰石
,
316L不锈钢纤维
,
热等静压
魏洪亮
,
杨晓光
,
于慧臣
材料工程
doi:10.3969/j.issn.1001-4381.2005.04.011
针对涡轮盘用GH4169合金开展了高温下单调拉伸、对称循环及非对称循环的实验工作,结果表明,该材料具有比较明显的循环软化和平均应力松弛特性.采用带Ohno/Wang修正的Chaboche粘塑性理论本构方程,对其表现出的复杂力学现象进行本构建模,介绍了Levenberg-Marquadt非线性优化算法,结合材料实验数据并通过该算法识别了本构方程参数,将本构方程通过用户子程序嵌入到有限元软件ABAQUS中,对GH4169合金的上述实验现象进行了数值模拟,计算曲线与实验曲线取得了较好的一致性.
关键词:
循环软化
,
平均应力松弛
,
本构方程
,
参数识别
Journal of Applied Physics
While the magnetic ground state associated with the step-like magnetization in Ca3Co2O6 remains to be an issue under debate, we investigate the effect of dipole dipole (D D) interaction on the magnetic ground state using the Wang-Landau algorithm. It is revealed that the D D interaction is equivalent to an effective short-range interaction term. An inclusion of this term allows a columnar-state platform and a 1/2 platform in addition to the two-step feature in the magnetization in response to magnetic field, suggesting that the role of the D D interaction in modulating the multistep magnetization in Ca3Co2O6 is non-negligible although our model may not reproduce all the experimentally observed effects. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676415]
关键词:
one-dimensional ca3co2o6;density-of-states;compound ca3co2o6;algorithm;crystal
