时间相关的含缺陷材料的流变破坏理论

含缺陷物体的与时间相关的失效过程是一个热力学开放的，远离平衡态的系统，失效过程中发生耗散结构的自组织现象，不同尺度上耗散结构的自相似性可供从微观过度到细观和宏观，基于缺陷演化过程国局域温度场和热磁效应的实验研究，从统一的宏、细、微观层次体系出发。研究了与时间相关的缺陷体的失效过程，结果表明。这个失效过程并非纯力学过程，其中的热力耦合和热磁效应不容忽略。     

Phase field simulation of interatomic potentials for double phase competition during early stage precipitation

Phase field model was employed to study the variations of interatomic potentials of Ni 3 Al (L1 2 phase) and Ni 3 V (DO 22 phase) as a function of temperature and concentration. The long-range order (LRO) parameter related interatomic potentials equations formulated by Khachaturyan were utilized to establish the inversion equations for L1 2 and DO 22 phases, with which interatomic potentials could be calculated. The interatomic potentials of Ni-Al and Ni-V exhibited approximately linear increases and decreases, individually, with enhanced Al concentration. Substituting the inverted interatomic potentials into the microscopic phase field equations led to three cases of precipitation sequence: the DO 22 phase preceded L1 2 phase precipitating at the interatomic potentials of Ni-V > Ni-Al; the vice cases; and two phases precipitated simultaneously at interatomic potentials of Ni-V and Ni-Al were equal.     

一种计算原子势函数的方法

对固体材料中原子间的简单相互作用函数Ｕ（ｒ）＝提出了一种计算方法．对立方晶系固体材料，使用实验测得的弹性系数Ｃ１１、Ｃ１２和Ｃ４４及体弹性模量Ｋ的实验测定值，通过网格求极值的方法，进行了计算机模拟．用该法计算出的势函数参量ｍ，ｎ，ａ，ｂ与其它方法估计结果基本一致．     

离子型固体的体积热膨胀系数，体积模量和原子间距与温度的函数关系

研究了16种离子型固体在室温到熔点之间的体积热膨胀系数、体积模量和原子间距．根据温度高于Debye温度时，Anderson—Griineisen参量与温度无关的近似，得到α(T)、BT(T)和r(T)的函数式以及一个唯象态方程．计算结果与实验数据一致．     

Atomistic simulation of rare earth-transition intermetallic compounds derived from CaCu5 type

The rare earth(R)-transition metal(M) compounds are important subjects of new functional materials. In this paper, first we review the transformation relations between R-M compounds (Rn-mM5n+2m) derived from CaCu5 type structure, and discuss their validity and limitations. Then we calculate the lattice parameters and crystal structures of five binary compounds, SmFe5, Sm2Fe17(H), Sm2Fe17(R), SmFe12(t), and Sm3Fe29 by energy minimization. With above results, we get the vector transformation matrix in reciprocal space in comparison with the traditional transformation matrix and analyze the reason for their similarity and difference. Finally, we discuss the stable effect of the third elements Cr, Ti to Sm3Fe29. The third elements also change the lattice parameters and the materials' X-rays diffraction pattern. The tradition matrix cannot reflect these differences.     

原子间相互作用对势计算合金奥氏体结合能

利用量子化学从头计算方法和半经验原子间相互作用对势,并参考“固体与分子经验电子理论”中的合金奥氏体的晶胞模型,计算出Fe-C-Mex奥氏体晶胞的结合能信息.由计算分析可知:(1)各种合金元素原子与C原子之间的结合能高于或低于Fe-C之间的结合能.由于这种差别,不同合金元素原子在固态相变中的特征行为也不同.(2)合金奥氏体中所有合金元素原子与C原子的结合能几乎都高于奥氏体中的Fe-Fe、C-C、Mex(Mey)-Mex(Mey)、Mex(Mey)-Mey(Mex)、Fe-Mex(Mey)原子之间的结合能.(3)相对γ-Fe基体而言,含有碳原子和合金元素原子的晶胞均具有较大的结合能,起固溶强化作用,而且结合能越大,对相变的阻力也越大.这种阻力和相变驱动力交互作用能改变相变产物的结构、形态和性能.     

含缺陷流变性材料破坏过程中宏、细、微观层次体系的一个统一方程

固体的不可逆形变和断裂与一类过程相关,在此过程中宏观效应是细观层次行为起着支配作用。因此,流变性材料在外力作用下的可靠预测应基于对细,微观层次中过程机理的清楚了解。显然,考虑到微,细、宏观层次中不同过程的间的相互作用,并在单一体系内对这些过程进行描述,才能够提供含缺陷流变性材料形变和断裂的充足理论。本文首次提出含缺陷流变性材料破坏过程中宏,细、微观层次体系的一个统一的方程。     

分子动力学中势函数研究

选用合适势函数来描述系统内原子间的相互作用是进行分子动力学模拟的基础.本文概要回顾了历史上出现的各种原子间互作用势函数.对各种势模型的理论背景、具体形式、应用范围、特点进行了分析评述.     

原子尺度上的波

提出全同粒子以及虚粒子假设,并推导了二维速度控制条件,再结合原子势函数,在原子尺度上描述了线性波的传播。考虑晶格非谐性以及位错的影响,进一步探究了二阶非线性波的产生机理。理论分析表明,晶格非谐性和位错引起的晶格畸变会诱发产生高阶虚粒子,高阶虚粒子是高阶非线性波产生的关键因素,位错等材料早期非线性或细微损伤导致高阶虚粒子增多而引发明显的高次谐波,因此,可以通过探测高次谐波诊断材料早期损伤。     

Site preference of ternary additions in Ni3Al

The substitution behavior of ternary additions in Ni3Al is systematically studied using interatomic potentials. The pair potentials between identical and distinct atoms are obtained via strict lattice inversion based on the first-principle cohesive energy curves. Taking long-range interaction into account, the quantitative calculations for the alloys containing various amounts of alloying elements are made by utilizing a relaxed sample averaging method. The relative magnitudes of cohesive energy corresponding to different configurations are used. The calculated results are in good agreement with the results of experiments. Finally, some predictions are made for the substitution behavior of certain alloying elements and some elements in the region of surface and interface that have not been previously studied.