A.A.Al-Aql
,
M.S.Al-Salhi
,
M.I.Ansari
材料科学技术（英文）
Precipitation study was carried out in Ni-35 at. pct Cr alloy by measuring electrical resistivity at different ageing temperatures and long ageing times. During ageing, it was observed that electrical resistivity initially rose with ageing time and then fell after very long ageing at a constant temperature. The initial increase in resistivity during ageing may be attributed to the formation of GP zones/Cr-rich precipitates at early stages by nucleation process and decrease in resistivity, and after attaining a maximum, is due to the growth of precipitate particles and subsequently by coarsening of these precipitates. The results of electrical resistivity measurements during ageing were confirmed by X-ray diffraction analysis indicating the formation of a Cr-rich phase and a Cr3Ni2 phase in the Ni matrix.
关键词:
Precipitation
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null
,
null
,
null
,
null
Journal of Materials Research
MAX-phase carbides (M is an early transition metal, A is an A-group element) exhibit an interesting bonding characteristic of alternative stacking of strong M-C bonds and relatively weak M-A bonds in one direction. In the present first-principles total energy calculations, we establish the relationship between mechanical properties and electronic structure for ternary M(2)AC (M = Ti, V, Cr. A = Al, Si, P, S) carbides. By systematically tuning elements on the M and A sites, pronounced enhancements of bulk modulus, elastic stiffness, and ideal shear strength are achieved in V-containing V(2)AC (A = Al, Si, P, and S) carbides. It is suggested that tailoring on the A site is more efficient than on the M site in strengthening the mechanical properties of studied serial carbides. The results highlight a general trend for tailor-made mechanical properties of ternary M(2)AC carbides by control of chemical bonding.
关键词:
strength;solids;shear;dislocations;ti3sic2
张建
,
秦晓英
,
李地
,
辛红星
,
宋春军
材料科学与工程学报
层状结构TiS_2具有准二维结构,高热电势(室温时S≈250μV/K)和大的热电功率因子,作为热电材料具有很好的开发和应用前景.通过固相反应法,我们分别用原子量大于和小于Ti的原子部分替代Ti位引入替位缺陷(Ni_(Ti)",Al_(Ti)',Mg_(Ti)"),合成了不同元素替代掺杂化合物M_(0.04)Ti_(0.96)S_2(M=Ni,Al,Mg),在5-310K的温度范围内研究了各化合物的电阻率、热导率及热电势率与温度的对应关系.结果表明Ni、Al、Mg三种元素的掺杂均引起了主体材料从金属性到半导体导电性质的转变,且在低温范围内呈现莫特二维变程跳跃电导规律,In σ∝T~(-1/3),表明了TiS_2的二维导电机制.值得注意的是:①Mg、Al的掺杂引起了热电势绝对值的显著增高,特别是Al掺杂的化合物在310K时热电势率为-500μV/K,达到了纯TiS_2的200%;②Ni掺杂也在整个研究温区引起热导率的明显下降,而Mg、Al的掺杂却在整个研究温区引起热导率的明显升高.由于电阻率的增大,Ni、Al的掺杂均没能使得材料的ZT值有所提高,而Mg的掺杂明显地提高了TiS_2的ZT值,在310K其ZT值是纯TiS_2的1.6倍.这表明元素掺杂是提高材料的热电优值的有效途径之一.
关键词:
TiS_2
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热电
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电阻率
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热导率
田兴
,
张彦生
,
师昌绪
金属学报
在Fe-Mn-Al-Cr系亚稳奥氏体区内,用膨胀法测定了40种合金的γ→ε-马氏体转变温度M_(es)。以多元线性回归方法处理实验结果,建立了M_(es)与合金成分关系的经验公式。经验公式中,1Wt-％的Al,C,Cr分别使Fe-Mn合金的M_(es)降低约51,339,8℃;这个结果与以前研究它们对Fe-Mn合金γ→ε-马氏体转变的影响和Ishida计算它们对Fe-Mn合金γ→ε相变驱动力的影响一致。根据γ→ε-马氏体转变的层错机制,简要讨论了Al,C和Cr对Fe-Mn合金M_(es)的影响。
关键词:
吴建新
,
江伯鸿
,
徐祖耀
金属学报
研究了母相平均晶粒尺寸和有序度对Cu-25.62Zn-3.97Al-0.0018B(wt-％)形状记忆合金热弹性马氏体相变点的影响。从相变热力学出发,得到马氏体相变点和晶粒尺寸的平方根的倒数成线性关系,并且随晶粒尺寸增大,马氏体相变点升高,与电阻法测得的结果符合很好。运用Landau理论,得到马氏体相变点和母相有序度的定量关系式,与X光衍射和电阻法试验的结果符合较好。求得试验用合金母相DO_3有序化的激活能约为46kJ/mol。
关键词:
Cu-Zn-Al合金
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shape memory alloy
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thermoelastic martensite
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grain size
,
ordering degree
Ruijie ZHANG
,
Zhi HE
,
Zhongwei CHEN
,
Wanqi JIE
材料科学技术（英文）
A method to predict the solid-liquid interface stability during unidirectional solidification is developed by coupling M-S model with CALPHAD method. The method was applied to Al-0.38 Zn and Al-0.34 Si-0.14 Mg (wt pct) alloys, and the predicted results were compared with some former experimental data of the two alloys. The good agreement between the calculation results and the experimental data demonstrates the superiority of the present method to the classical one based on constant parameter assumptions.
关键词:
Interface stability
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null
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null
WU Jianxin JIANG Bohong XU Zuyao (T.Y.Hsu) Shanghai Jiaotong University
,
Shanghai
,
China Associate Professor
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Dept.of Materials Science and Engineering
,
Shanghai Jiaotong University
,
Shanghai
,
China
金属学报(英文版)
The effect of grain size and ordering of the parent phase on the critical points of thermoelastic martensitic transformation in Cu-25.62 Zn-3.97 Al-0.0018 B(wt-%)shape memory alloy has been investigated.Based on the thermodynamics of phase transformation,a linear rela- tionship between the starting temperature of martensitic transformation and the reciprocal of the square root of grain size is obtained,i.e.M_s temperature rises with increasing grain size. It shows a good agreement with the results of electric resistance measurement.Applying the Landau's theory,a quantitative relationship between M_s and the ordering parameter of the parent phase is set up,which is well confirmed by the results of X-ray diffraction and electric resistance measurement.The activation energy of the ordering process in the parent phase of the alloy is calculated to be 46 kJ/mol.
关键词:
Cu-Zu-Al
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null
,
null
,
null
,
null
Materials Letters
Secondary M,C precipitation was investigated in K40S cobalt-base alloy after 100 h aging at 950 degreesC. The results showed that it was closely related to the tungsten-rich zones inherited from the as-cast condition and the degeneration of the primary M7C3 carbide. A direct element reaction, 6M + C --> M6C, in which C comes from the decomposition of the M7C3 carbides, is suggested as the mechanism of secondary M6C precipitation in K40S alloy. (C) 2001 Elsevier Science B.V. All rights reserved.
关键词:
M6C precipitation;aging;M7C3 carbide;superalloy
汪洁
,
包小倩
,
高学绪
,
张茂才
,
朱洁
,
张从阳
金属功能材料
采用真空快淬设备以辊速5 m/s、10 m/s、15 m/s、20 m/s、30 m/s制备了Nd60Fe30M10(M=Al,Si,Ga)系的.非晶带",研究了制备速度对"非晶带"永磁性能和结构的影响.实验结果表明:Nd60Fe30Si10和Nd60Fe30Ga10同经典合金Nd60Fe30Al10一样,也显示出非晶永磁性能,并且比相同条件下制备的Nd60Fe30Al10"非晶带"的永磁性能更好;三种"非晶带"的矫顽力随辊速的降低而提高.对Nd60Fe30Al10"非晶带"的TEM分析表明,以30 m/s辊速制备的"非晶带",有2～5 nm的析出物弥散分布在非晶基体上;而以5 m/s辊速制备的"非晶带",有10 nm左右和150～200 nm的析出物分布在非晶基体上.析出物的生成,促进了矫顽力的提高.
关键词:
Nd60Fe30M10合金
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非晶带
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永磁性能
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组织结构
汪艳宁
,
张智超
,
苑宏英
,
靖大为
膜科学与技术
doi:10.16159/j.cnki.issn1007-8924.2016.06.003
以反映管道压降的系统模拟软件为工具,以特定基准系统参数及2 m/s管道流速为基础,分析了各种径流方向组合的反渗透系统运行工况,提出了全壳产水量与全壳错流比两个分别表征各壳元件污染速度与清污力度的运行指标,证明了各壳元件产水量失衡是其污染失衡的主要原因,明确了目前工程中常用的2 m/s流速管道系统中底层膜壳污染最重.
关键词:
反渗透系统
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管道压降
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径流方向
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污染分布
