Computer generation of binary and ternary phase diagrams via a convex hull method

A rapid computational technique for determining equilibrium phase diagrams of multicomponent systems by constructing the convex hull of the free energy surface is introduced. Rather than calculating tangent lines or planes, this method guarantees a convex representation of the equilibrium free energy surface on a discrete set of points in composition space. Although the accuracy of these phase diagrams is limited by the spacing of points, there are no restrictions on the number or types of free energy functions that may be considered; functions with singular or unknown derivatives may even be used. This method is then applied to generate several model binary and ternary phase diagrams. This paper was presented at the International Phase Diagram Prediction Symposium sponsored by the ASM/MSD Thermodynamics and Phase Equilibria Committee at Materials Week, October21–23,1991, in Cincinnati, Ohio. The symposium was organized by John Morral, University of Connecticut, and Philip Nash, Illinois Institute of Technology.     

Evaluation of sphericity error from form data using computational geometric techniques

The measurement data for evaluation of sphericity error can be obtained from inspection devices such as form measuring instruments/set-ups. Due to misalignment and size-suppression inherent in these measurements, sphericity data obtained will be distorted. Hence, the sphericity error is evaluated with reference to an assessment feature, referred to as a limacoid. Appropriate methods based on the computational geometry have been developed to establish Minimum Circumscribed, Maximum Inscribed and Minimum Zone Limacoids. The present methods start with the construction of 3-D hulls. A 3-D convex outer hull is established using computational geometric concepts presently available. A heuristic method is followed in this paper to establish a 3-D inner hull. Based on a new concept of 3-D equi-angular line, 3-D farthest or nearest equi-angular diagrams are constructed for establishing the assessment limacoids. Algorithms proposed in the present work are implemented and validated with the simulated data and the data available in the literature.     

凸包U型零件成形工艺及模具设计

通过对凸包U型零件结构特征、生产条件及传统工艺的分析,指出了传统工艺流程在加工该类零件时的不足,并根据当前生产条件确定了凸包U型零件的成形方法及设计了具有显著特点的凸包成形模具。按照确定的工艺及模具工作流程进行生产,最终保证了零件成形质量,提高了生产效率。     

正列密集方形凸包件啮辊胀形数值模拟

通过提供单元凸、凹模的设计要点,使用Deform-3D软件对板料进行模拟分析,在长度为100 mm、宽度为130 mm、厚度为1 mm的塑性板料上,尝试模拟成形5列4排(纵横对正)、边长b=10 mm、高度h≤3.5 mm的正列密集方形凸包件.从啮辊胀形装置、凸包尺寸参数两个方面进行模拟研究,首先论证了压料框的必要性,...     

Development and application of convex hull in the assessment of roundness error

The roundness error for minimum circumscribed circle (MCC) and maximum inscribed circle (MIC) from coordinate data is obtained according to the distance between the two parallel lines. The lines for MCC and MIC can be found based on convex hull and polar coordinates and be determined by four critical measured points that lead to an efficient way to solve the roundness error. In this paper, an approach for constructing a convex hull is presented using vector product. The method developed is implemented and validated with the data available in the literature.     

Application of convex hull in the assessment of roundness error

The concept of the Minimum Zone Lines is proposed as a determinant condition of the minimum zone circle. The minimum zone roundness error from coordinate data is obtained by the distance between the Minimum Zone Lines. The Minimum Zone Lines determined by four critical measured points can be constructed based on convex hull and coordinates transmission. The rapid selection of iteration points with convex hull leads to an efficient way to solve the minimax solution. The objective of this strategy is to pick out the critical data points as early as possible so that the redundant data points can be rejected. The method developed is implemented and validated with the data available in the literature.     

三维自组装膜的制备及其摩擦磨损试验

利用二甲基亚砜(DMSO)对高岭土进行改性,通过原位聚合反应制备PET/高岭土纳米复合材料.为便于自组装,利用高分子网络凝胶法的空间限域作用制备单分散性PET/高岭土复合微球,并利用改进的蒸发诱导自组装法(EISA)制备出具有均匀凹坑/凸包微结构分布的IPN聚合物/PET/高岭土薄膜,通过正交试验法研究了微球平均粒径、...     

顶罩板翻边翻孔压凸包模设计

介绍了顶罩板翻边翻孔压凸包模的结构,模具解决了顶罩板的边内翻后卸料问题。实践证明,模具结构设计合理,使用寿命长,满足零件批量生产要求,对同类模具的设计有一定参考作用。     

Mo-Si-C系金属间化合物Mo_5Si_3C Gibbs生成自由能估算

根据最小自由能原理和向下凸曲面性质推导出估算三元系和二元系金属间化合物热力学数据的判断式 ,并以 Mo- Si- C三元系为例 ,估算了三元相 T(Mo5 Si3C)的 Gibbs生成自由能。     

MIC公司的钛白生产及战略

根据最小自由能原理和向下凸曲面性质推导出估算三元系和二元系金属间化合物热力学数据的判断式,并以Mo-Si-C三元系为例,估算了三元相T（Mo5Si3C）的Gibbs生成自由能。     

First-principles phase stability and elastic properties of Al–La binary system intermetallic compounds

The phase stability and the elastic properties of Al–La binary system intermetallic compounds were thoroughly investigated using first-principles calculations. Firstly, the 0 K phase diagram for this system was calculated using the formation enthalpy convex hull construction, which indicates three metastable phases, namely Al₄La (I4/mmm), Al₄La (Imm2), and AlLa₃ (Pm-3m). Then, the stability of Al₁₁La₃ was examined at temperatures lower than 1000 K compared with the two Al₄La allotropes and the Al + Al₂La two-phase equilibrium. The results demonstrate that the needlelike phase in Mg–Al–La based alloys should be indexed as Al₁₁La₃, which is thermodynamically stable, with no decomposition under aging. Thirdly, AlLa₃ (Pm-3m) is more stable than AlLa₃ (P63/mmc) at temperatures higher than approximately 590 K, which well agrees with the experimental results. Finally, the elastic properties and vibrational properties for the stable Al–La intermetallic phases were calculated in this work.     

横向连接板冲压工艺与模具设计

通过对形状复杂的汽车覆盖件横向连接板的冲压工艺分析,将多个工序内容均分到几个复合工序中,通过计算、试冲、修正的方法探索出坯料尺寸轮廓确定方法,通过两次成形和中间预制孔解决了异形凸包拉裂问题,最后设计了合理的模具结构,完成了产品的冲压。     

失稳分解组织演化和粗化动力学的晶体相场法研究(英文)EI北大核心CSCD

以二元对称与非对称合金的调幅分解为研究对象,采用晶体相场模型从沉淀相演化和粗化机制两方面分析合金的失稳分解。研究表明,当合金的成分由对称点向非对称点转变时,沉淀相形貌逐渐由长条形过渡为球形;后期粗化机制由邻近颗粒的合并机制转变为Ostwald熟化机制;只有当二元合金的成分接近于失稳线时,其粗化动力学才较好地与修正的LSW理论符合。     

A phase-field model with antitrapping current for multicomponent alloys with arbitrary thermodynamic properties

The development of accurate and efficient computational tools for phase transformation is a prerequisite in order to predict the microstructure evolution during phase transformation in engineering alloys. Even though the antitrapping phase-field model (PFM) has been developed and is increasingly being used for this purpose, it has been limited to dilute binary alloys. In this study, the antitrapping PFM was extended to multicomponent systems with arbitrary thermodynamic properties. We showed that at the condition of vanishing chemical potential jump, the antitrapping term in the multicomponent diffusion equation remains unchanged with the case of binary dilute alloys. We then derived the relationship between the phase-field mobility and the real interface mobility at the thin interface limit, and showed that the multicomponent effect in the relationship can be expressed in a concise matrix form.     

电弧喷涂新型底层材料-Ni-Al合金的研究

利用镍铝三元相图分析了铝含量对制备镍铝合金丝的含量,通过ｘ射线衍射结果研究了合金丝材及电弧喷涂镍铝合金涂怪的相结构,测定了涂层与基体的结合强度,用线扫描测出涂层与基体间元素的扩散,分析了涂层与基本间造成高结合强度及形成扩散的原因。     

电弧喷涂新型底层材料-Ni-Al合金的研究

利用镍铝二元相图分析了铝含量对制备镍铝合金丝的影响,通过Ｘ射线衍射结果研究了合金丝材及电弧喷涂镍铝合金涂层的相结构,测定了涂层与基体的结合强度,用线扫描测出了涂层与基体间元素的扩散,分析了涂层与基体间造成较高结合强度及形成扩散的原因。     

First-principles phase stability calculations and estimation of finite temperature effects on pseudo-binary Mg6(PdxNi1−x) compounds

The stability of pseudo-binary Mg₆(Pd_xNi_1?x) compounds has been studied at T = 0 K via first-principles calculations and at 673 K by thermodynamic modelling of finite temperature effects. At 0 K, these compounds are not stable since their formation energy is above the convex hull defined by the Mg, Mg₂Ni and Mg₆Pd phases, although the energy difference is not very high. However, at 673 K, vibrational and configurational entropic effects allow the stabilisation of some of the calculated pseudo-binary Mg₆(Pd_xNi_1?x) compounds. The vibrational contribution to the thermodynamic properties of the studied compounds has been calculated from Debye temperatures in the harmonic approximation. Also, the configurational entropy has been estimated taking into account the possible distribution of Pd and Ni between the several sites available in the pseudo-binary structure. The identification of intrinsic disorder and the associated energies and entropy are innovative features of this work. The phase diagram at the Mg-rich corner derived from these calculations is in fairly good agreement with recently published experimental results. In addition, the Ni for Pd substitution has been studied for the several sites available for Pd in the binary Mg₆Pd compound. The calculated preferential site occupancy is in agreement with the site occupancy factors determined in recent neutron diffraction experiments.     

Calculated phase diagrams of aluminum alloys from binary Al–Cu to multicomponent commercial alloys

More than three decades have passed since the publication of Alan Prince’s book on multicomponent phase equilibria. The most significant development in this time has been the use of a combined computational/experimental approach to calculate multicomponent phase diagrams. This has led to important advances in the design and processing of structural and functional materials for practical applications. In this paper, we present a few examples focusing on aluminum alloys from the classical Al–Cu binary to multicomponent alloys with a view toward practical applications.     

Delineation of the space of 2-point correlations in a composite material system

The complete set of 2-point correlations for a composite material system with a large number of local states (e.g. polycrystalline metals) forms a vast and unwieldy data set containing a large amount of redundant information. The interrelations in these correlations have been well characterized for composite material systems with two local states, but only a small number have been delineated for the composite systems with many local states. This paper presents an analysis of interrelations between the complete set of 2-point correlations for composite material systems through their spectral representations via discrete Fourier transforms. These interrelations are used to delineate a compact and convex space that bounds the set of all physically realizable 2-point correlations called the 2-point correlations hull. The representation of any given microstructure in this hull, and the techniques to produce a representative volume element are also explored in this paper.     

CALCULATION OF ACTIVITIES IN In-As AND Ga-As SYSTEMS

本文用变通的Gibbs-Duhem关系式,通过θ函数进行积分变换,并根据相图,结合化合物生成自由能与温度的关系式,得到了一个判别生成自由能是否准确的方法.然后据此对有关数据进行了选择,并计算In-As,Ga-As两个二元系中组分的活度.与文献数据相比较,本文结果较为合理.