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运用密度泛函理论的第一性原理计算分析了MgZn2相的电子结构及相关磁性质。能带结构和态密度分析表明Zn4s和Zn4p轨道、Mg3s和Mg3p轨道分别发生sp态杂化,然后杂化态之间相互作用而形成Zn-Mg键;Mulliken布居分布计算显示:Zn1-Mg(Zn1是处于晶格边缘的Zn原子)和Zn2-Mg(Zn2是处于晶格内部的Zn原子)电子云重叠布居数接近0,电子密度分析显示Zn-Mg之间电子密度分布具有明显的定域性。结合上述结果与Zn、Mg原子的电负性差异,确定Zn-Mg键为极性共价键。分态密度(PDOS)分析显示,Zn1-Mg键和Zn2-Mg键的差异主要表现在Zn24s轨道在-10~-6 eV区域对成键的贡献度高于Zn14s轨道,而Zn14s轨道在2~5 eV区域对成键的贡献度高于Zn24s轨道。进一步对MgZn2的积分自旋态密度和磁矩计算表明:MgZn2磁性质表现为顺磁性,其磁性主要来源于Zn1-Mg键中的2个自旋相同的未配对电子;MgZn2的顺磁性特性将使Al-Zn-Mg-Cu(7xxx系)高强铝合金产生磁致塑性效应。 相似文献
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Tensile properties and microstructure of 2024 aluminum alloy subjected to the high magnetic field and external stress 下载免费PDF全文
In order to explore the dependence of plasticity of metallic material on a high magnetic held,the effects of the different magnetic induction intensities(H = 0 T,0.5 T,1 T,3 T,and 5 T) and pulses number(N = 0,10,20,30,40,and 50) on tensile strength(σ_b) and elongation(δ) of 2024 aluminum alloy are investigated in the synchronous presences of a high magnetic held and external stress.The results show that the magnetic held exerts apparent and positive effects on the tensile properties of the alloy.Especially under the optimized condition of H~*=1 T and N~*=30,the σ_b and 8 are 410 MPa and 17% that are enhanced by 9.3% and 30.8% respectively in comparison to those of the untreated sample.The synchronous increases of tensile properties are attributed to the magneto-plasticity effect on a quantum scale.That is,the magnetic held will accelerate the state conversion of radical pair generated between the dislocation and obstacles from singlet to the triplet state.The bonding energy between them is meanwhile lowered and the moving flexibility of dislocations will be enhanced.At H~* = 1 T and N~* = 30,the dislocation density is enhanced by 1.28 times.The relevant minimum grain size is 266.1 nm,which is reduced by 35.2%.The grain rehning is attributed to the dislocation accumulation and subsequent dynamic recrystallization.The(211) and(220) peak intensities are weakened.It is deduced that together with the recrystallization,the hne grains will transfer towards the slip plane and contribute to the slipping deformation. 相似文献
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运用数学归纳法,Gronwall不等式及方程的守恒量等工具,研究组合KdV方程初值问题解的有界性.首先在schwartz空间得到了方程解及解的任意阶导的上确界可以由初值为变量的图灵可计算函数来控制,由于schwartz空间S(R)是Sobolev空间Hs(R)(s≥0)的稠子空间,结果可以直接推广到sobolev空间Hs(R)(s≥0),所以组合KdV方程解在Hs(R)(s≥0)上确界可以由一个可计算函数来控制,从而为研究解算子的可计算性并运用图灵机计算组合KdV方程的解奠定了基础. 相似文献
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Heck reaction of iodoarenes with methyl acrylate, catalyzed by cyclolmlladated complexes of tertiary arylamines, was investi-gated in ionic liquid 1-butyl-3-metylimidazolium tetratluorobo-rate ([Bmim] BF4^- ). The products can be isolated convenient-ly from the ionic liquid-catalyst system. The catalysts could be reused for more than 10 times still with satisfactory catalytic ac-tivity. 相似文献
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Homocoupling of aryl iodides catalyzed by cyclopalladated complexes of tertiary arylamines gives symmetric biaryls with good yields in DMA or ionic liquid [Bmim]BF4. This catalytic alternative of the Ullmann reaction has proved to be sensitive to both electronic and steric factors of substrates. 相似文献
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研究强磁场对AZ31镁合金塑变能力和微观组织的作用,在3 T脉冲强磁场条件下对合金进行磁场耦合应力时的拉伸实验.采用电子背散射衍射、Ⅹ射线衍射和透射电镜分析等方法研究材料的微观组织.结果表明:与0 T拉伸试样相比,3 T拉伸试样抗拉强度和延伸率分别提高了2.2%和28.7%,说明将强磁场耦合作用于材料塑性变形过程时,能在不降低材料强度的同时提高镁合金的塑性变形能力,有助于同步改善材料强韧性.磁场作用机理主要表现为磁致塑性效应,计算表明主要合金相β(Mg_(17)Al_(12))为顺磁性,有助于发挥磁场作用效果.磁场提高了位错运动灵活性并促使位错增殖,晶界处位错堆积和应力集中促进了再结晶形成,晶粒发生细化,发挥细晶强韧化效果;同时磁场诱发塑性变形时的晶粒转动,新生成非基面取向的晶粒弱化了镁合金(0001)基面织构,该组织特征有助于提高材料的塑变能力. 相似文献
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运用密度泛函理论的第一性原理计算分析了MgZn2相的电子结构及相关磁性质。能带结构和态密度分析表明Zn4s和Zn4p轨道、Mg3s和Mg3p轨道分别发生sp态杂化,然后杂化态之间相互作用而形成Zn-Mg键;Mulliken布居分布计算显示:Zn1-Mg(Zn1是处于晶格边缘的Zn原子)和Zn2-Mg(Zn2是处于晶格内部的Zn原子)电子云重叠布居数接近0,电子密度分析显示Zn-Mg之间电子密度分布具有明显的定域性。结合上述结果与Zn、Mg原子的电负性差异,确定Zn-Mg键为极性共价键。分态密度(PDOS)分析显示,Zn1-Mg键和Zn2-Mg键的差异主要表现在Zn24s轨道在-10~-6eV区域对成键的贡献度高于Zn14s轨道,而Zn14s轨道在2~5eV区域对成键的贡献度高于Zn24s轨道。进一步对MgZn2的积分自旋态密度和磁矩计算表明:MgZn2磁性质表现为顺磁性,其磁性主要来源于Zn1-Mg键中的2个自旋相同的未配对电子;MgZn2的顺磁性特性将使Al-Zn-Mg-Cu(7×××系)高强铝合金产生磁致塑性效应。 相似文献