马氏体相变的界面吸引子模型

从经典的马氏体相界面运动方程出发,利用相平面分析,证明具有界面摩擦的马氏体相界面是吸引子,与理想的马氏体相界面的孤立子特征不同.通过对非线性方程解的分析,得到发生应力诱发马氏体相变的相界面趋向为焦点型定常吸引子,而热诱发相变的马氏体相界面趋向为结点型定常吸引子,因此考虑界面摩擦后相界面的运动与理想相界面的运动具有不同的非线性特征.     

The influence of temperature on stacking fault energy in Fe-based alloys

Temperature has great influence on the stacking fault energy (SFE). Both SFE and dr0/ d T for Fe-based alloys containing substitutional or interstitial atoms increase with increasing tempera-ture. Based on the thermodynamic model of SFE, the equation dr0/dT=drcn/dT+drseg/dT+drMG/dT and thoseexpressions for three items involved are established. The calculated dr0/dT is generally consistent with the experimental. The influence of chemical free energy on the temperature dependence of SFE is almost constant, and is obviously stronger than that of magnetic and segregation contributions. The magnetic transition and the segregation of alloying elements at stacking faults cause a decrease in SFE of the alloys when temperature increases; that is, drMG/dT<0 and dyseg/dT<0. Meanwhile, such an influence decreases with increasing temperature, except for the drseg/d 7 of Fe-Mn-Si alloys. With these results, the experimenal phenomena that the SFE of Fe-based alloys is not zero at the thermo-dynamically equilibrated tem     

形状记忆合金中的马氏体变体在外场下的再取向和再分布机制

利用相场方法研究了马氏体变体在循环应力作用下再取向和再分布的微观机制。模拟结果表明,随着外应力的增加,在孪晶界面会出现母相的形核和长大,以此实现变体间的转化,这是3种变体转化为2种变体的主要再取向机制;卸载后消失的变体在孪晶界面重新形核并长大以完成系统内微观组织的再分布。在Mn-Cu合金中这种机制是控制循环载荷下形状记忆效应产生的主要机制。     

Electronic structure of FCC phase in Fe-Mn-Si based shape memory alloys and its stability

The relationship between the electronic structure of FCC phase in Fe-Mn-Si alloy and its stability has been studied by using the discrete variational method based on the first principle. The reason why Mn and Si elements have different influences on the stacking fault energy may be related to the electron concentration ( e/a). Si reduces the hole number of 3d band while Mn is rather complicated . The binding energy has been calculated and the experimental results that martensite start temperature (Ms) varies with Si and Mn are explained. When the external stress is exerted in three directions, the electronic structure, the total density of states, the energy gap at Fermi energy level( EF) and the energy degeneracy will change into other states. When the different external stresses are exerted in one direction, 3d or 4s orbital occupations of the central atom decrease, the partial density of states seems to be thinner and its peak increases at EF, the bond orbit shrinks in the direction of the external st     

�ۻ�����þ�ı����ɷּ��ṹ����

 通过在钝化液中加入一种稀土氧化物制备成一种钝化镁粒，用SEM、XRD、AES分析了这种自制钝化镁粒表面层的成分和结构，发现其表面包覆均匀，致密，XRD和AES结果显示表面层主要含有CeO2和MgO。通过线扫描分析元素浓度沿包覆层方向的变化，大致估算了包覆层的厚度为7~8 μm。经测试其在1〖KG-*9〗000 ℃下的阻燃时间达到了25.7 s，较普通钝化镁粒阻燃时间有所提高。     

Fe-Mn-Si合金相变热滞的理论计算

利用相变热力学和界面摩擦概念，推导出Fe-Mn-Si合金相变热滞（As-Ms）的一般计算表达式；根据此关系式，计算了这种合金的相变热滞，计算结果与实验值相符，合金的界面摩擦能耗比较大，且与合金的热滞成正比，由此可知合金的热滞大是由于界面摩擦能耗大所造成的。     

马氏体预相变的临界驱动力及非线性特征

基于电子-声子相互作用计算了马氏体预相变的临界驱动力．计算结果表明,临界相变驱动力的大小和凝聚声子的能量处于同一数量级．充分考虑这种相互作用和声子软化,得到关于原子位相角的double sine-Gordon方程,以此分析预相变的非线性特征,并认为电子-声子耦合机制可作为预相变的形核机制．     

Fe-30Mn-6Si-xN形状记忆合金层错能的热力学计算

利用包含置换原子和间隙原子的层错能热力学模型,计算了不同Ｎ含量下Ｆｅ－３０Ｍｎ－６Ｓｉ－ｘＮ形状记忆合金的层错能。计算结果表明,Ｎ对合金层错能的作用是先境加后降低（存在一个转折点Ｐ,对应Ｎ含量（质量分数）为ｗｐ）：当少量的Ｎ固溶在合金中（ｗＮ〈ｗｐ）时,由于Ｎ和近邻原子间的交互作用,合金的层错能有所增加;在Ｎ含量比较高时（ｗＮ〉ｗｐ）,Ｎ在层错区的偏聚对层错能的降低起了重要作用,Ｎ在合金中不同的间     

形状记忆合金中的马氏体变体在外场下的再取向和再分布机制(英文)

利用相场方法研究了马氏体变体在循环应力作用下再取向和再分布的微观机制。模拟结果表明,随着外应力的增加,在孪晶界面会出现母相的形核和长大,以此实现变体间的转化,这是3种变体转化为2种变体的主要再取向机制;卸载后消失的变体在孪晶界面重新形核并长大以完成系统内微观组织的再分布。在Mn-Cu合金中这种机制是控制循环载荷下形状记忆效应产生的主要机制。