基于热、动力学计算模拟研发梯度硬质合金

对于材料研发和过程参数优化来说,掌握材料体系的热、动力学信息并基于CALPHAD(相图计算)方法进行计算模拟是一种强有力且高效的方式.CALPHAD计算结果的准确性在很大程度上取决于热力学和动力学数据库的质量.基于前期建立的热力学数据库(CSUTDCC1)和动力学数据库(CSUDDCC1),对硬质合金研发过程中所关心的...     

Integrated Computational Materials Engineering in Solar Plants: The Virtual Materials Design Project

The high temperatures required for efficient operation of solar thermal power plants constitutes one of the major challenges of this technology. Gaining insight into materials behavior at very high temperatures is critical to improve their techno-economic feasibility. Standard material characterization approaches become inefficient, as extensive testing campaigns are required. We propose a multiscale–multiphysical approach that accounts for materials composition to (1) predict the behavior of both Inconel 625 and new solar salts, and (2) assess the thermomechanical performance of key components. We carried out a complete thermoelastic multiscale analysis that spans six time and length scales in a single simulation platform, combining discrete and continuum tools (from quantum to continuum mechanics). These applications show the substantial economic benefits that may be achieved by an ICME approach in the energy sector, reducing the cost of prototypes while decreasing development times and maintenance costs due to a better understanding of materials behavior.     

Application of ICME to Engineer Fatigue-Resistant Ni-Base Superalloys Microstructures

Critical rotating components used in the hot section of gas turbine engines are subject to cyclic loading conditions during operation, and the life of these structures is governed by their ability to resist fatigue. Since it is well known that microstructural parameters, such as grain size, can significantly influence the fatigue behavior of the material, the conventional processes involved with the manufacture of these structures are carefully controlled in an effort to engineer the resulting microstructure. For a commercial Ni-base superalloy, RR1000, the development of process models and deformation mechanism maps has enabled not only control of the resultant grain size but also the ability to tailor and manipulate the resulting grain boundary character distribution. The increased level of microstructural control was coupled with a physics-based fatigue model to form an integrated computational materials engineering framework that was used to guide the design of damage-tolerant microstructures. Simulations from a 3D crystal plasticity finite element model were used to identify microstructural features associated with strain localization during cyclic loading and to guide the design of polycrystalline microstructures optimized for fatigue resistance. Conventionally processed and grain boundary engineered forgings of a commercial Ni-based superalloy, RR1000, were produced to validate the design methodology. For nominally equivalent grain sizes, high-resolution strain maps generated via digital image correlation confirmed that the high density of twin boundaries in the grain boundary engineered material were desirable microstructural features as they contribute to limiting the overall length of persistent slip bands that often serve as precursors for the nucleation of fatigue cracks.     

Integrated Computational Materials Engineering of Titanium: Current Capabilities Being Developed Under the Metals Affordability Initiative

A technical review of the titanium model development programs currently funded under the Metals Affordability Initiative is presented. Progress of the “Advanced Titanium Alloy Microstructure and Mechanical Property Modeling” and “ICME of Microtexture Evolution and its Effect on Cold Dwell/High/Low Cycle Fatigue Behavior of Dual Phase Titanium Alloys” will be reviewed followed by a discussion of the future modeling needs of the aerospace industry.     

Reducing Vehicle Weight and Improving U.S. Energy Efficiency Using Integrated Computational Materials Engineering

Transportation accounts for approximately 28% of U.S. energy consumption with the majority of transportation energy derived from petroleum sources. Many technologies such as vehicle electrification, advanced combustion, and advanced fuels can reduce transportation energy consumption by improving the efficiency of cars and trucks. Lightweight materials are another important technology that can improve passenger vehicle fuel efficiency by 6?C8% for each 10% reduction in weight while also making electric and alternative vehicles more competitive. Despite the opportunities for improved efficiency, widespread deployment of lightweight materials for automotive structures is hampered by technology gaps most often associated with performance, manufacturability, and cost. In this report, the impact of reduced vehicle weight on energy efficiency is discussed with a particular emphasis on quantitative relationships determined by several researchers. The most promising lightweight materials systems are described along with a brief review of the most significant technical barriers to their implementation. For each material system, the development of accurate material models is critical to support simulation-intensive processing and structural design for vehicles; improved models also contribute to an integrated computational materials engineering (ICME) approach for addressing technical barriers and accelerating deployment. The value of computational techniques is described by considering recent ICME and computational materials science success stories with an emphasis on applying problem-specific methods.     

21世纪的航空航天材料(下)

<正> 先进燃气涡轮发动机用热强材料 材料在高温、应力及侵蚀性介质苛刻综合作用条件下有无工作能力的问题,是第六代发动机研制中最重要的问题。 第六代发动机必须保证推/重比达到20:1。第四代发动机(1970～1975年)的推/重比仅为8:1,第五代现代发动机(1985～2000年)的推/重比只达到10:1。 在此情况下,应该将气体温度提高300～400 K,使     

Computational Discovery,Characterization, and Design of Single-Layer Materials

Single-layer materials open up tremendous opportunities for applications in nanoelectronic devices and energy technologies. We first review the four components of a materials science tetrahedron for single-layer materials. We then provide a theoretical perspective of characterizing single-layer materials. This leads to a general data-mining process to predict and computationally characterize emerging single-layer materials. Finally, we comment on limitations and possible improvements of current computational procedures for the discovery, characterization, and design of single-layer materials.     

Computational Materials Science and Engineering Education: An Updated Survey of Trends and Needs

We present a summary of the state of computational materials science and engineering (CMSE) education based on a survey of materials science department chairs, faculty with computational interests, and employers of materials scientists and engineers. This survey is an update of one previously conducted in Thornton et al. (JOM 61:12–17, 2009). Three questionnaires were distributed among department chairs, faculty, and employers. The surveys asked to rate the importance of incorporating CMSE into the undergraduate curriculum, how it should be incorporated, the current offerings in CMSE, how those offerings have recently changed, what software tools are taught/used, and what opportunities exist in CMSE education, along with freeform questions regarding experience in teaching CMSE and impact of CMSE education. The survey results revealed an increased availability of CMSE courses in most of the materials departments surveyed, and strong support for including CMSE into the core curriculum. They also indicated that there is no clear preference as to whether such incorporation into the core curriculum should be through standalone courses or through modules in existing courses. The resources used in these courses, including online tools and software, are also summarized. The responses from the computational faculty point to a continued need for modules, including software tools and educational materials, that can be readily implemented by materials faculty regardless of their area of expertise.     

准晶、准晶凝固及其在材料工程上的应用(二)

正4准晶的特性和应用4.1准晶的主要特征[8]准晶如同许多金属间化合物一样,在室温时具有高的硬度和脆性,低的表面摩擦系数和高的抗磨损能力,主要是源于它的非周期性原子排列,它不象晶体材料那样具有周期平移序。有些准晶具有高的电阻,在室温下为100~300 mΩ/cm。它具有负的电阻温度系数和低的热传导系数,类似于许多非晶体材料和半导体合金材料。典型的准晶材料显示弱的     

准晶、准晶凝固及其在材料工程上的应用(一)

准晶是不具有三维周期平移序,而只具有准周期长程平移序和旋转对称性的新固体结构形态。Shechtman发现准晶使人们对晶体的认识发生了根本性变化。正是因为如此,原来的原子在空间的规则重复排列的晶体定义已改为具有本质的明锐衍射花样的任何固体。准晶绝大多数出现在Al基合金中。准晶按热力学稳定程度分亚稳相和稳定相。在自然界还存在着一些天然态准晶。为此,准晶可由熔体快速凝固或慢速凝固予以制造,并且可以应用Bridgman和Czochralski等方法制取准晶单晶。准晶具有一些独特的特性。准晶在材料工程上应用的核心点是在材料组织中出现准晶会使其力学性能得到提高。对铝基合金相应的方法可获得以准晶相为主体的组织和在固溶体的基体上出现准晶相。对钢铁材料是通过合金成分设计和热处理方法研究使在材料基体上弥散析出准晶相。     

面向并行工程的机床CAD/CAE信息集成系统研究

为实现跨网络跨平台的协同设计，建立了机床CAD/CAE信息集成系统框架，为了消除机床设计开发中各部分内部信息和数据间的矛盾和冗余，提出一种基于CORBA软总线的信息集成系统构架，实现了机床开发过程中内部信息和数据处理具有充分的及时性、准确性、一致性和共享性，实现了机床开发的并行式程，缩短产品开发周期、降低了产品开发的成本。     

A Mathematical Model for Determination of Lamellar Spacing in Materials of Poly-Grain Microstructures

基于多晶材料球形晶粒的假设合金相理论的基础上,建立了的计算两相片状组织表观值与真实值定量关系的数学模型。结果表明,对于多数多晶材料其晶粒尺寸远大于片间距,片间距的平均表观值与真实值的比可以由修正系数k表征。片间距与晶粒尺寸比值从0.05减小到0.0001,k从1.5391增加到1.5707,k值逐渐接近于π/2。当片间距与晶粒尺寸的比值小于0.001时,可以认为k为常数π/2。本模型比传统方法在得到真实片间距过程中减少了工作量。     

国家高技术产业化示范项目工程设计问题探讨

国家高技术产业化项目的工程设计是一个新的设计课题。和传统的项目工程设计相比 ,尽管设计程式相同 ,但具体设计有其全新的一面。笔者结合具体的设计项目 ,分析了设计院在进行国家高技术产业化项目工程设计中面临的问题 ,提出了解决问题的 4个方面 ,旨在引起广泛的关注 ,将该类项目设计工作做得更好。     

An Axiomatic Approach for “Target Cascading” of Parametric Design of Engineering Systems

Complex engineering system realization involves finding out design specifications that simultaneously achieve performance objectives at different levels. A common practice in industry is to adopt “Target Cascading” to obtain proper settings of the performance objectives, and find out those design specifications, not necessarily optimal, but satisfying all the desirable component-level, subsystem-level and system-level performance objectives. In this paper, an Axiomatic Approach to “Target Cascading” (AATC) is presented to improve the current “Target Cascading” process. AATC uses axioms to guide the decompositions of performance objectives, and an integration of a hybrid meta-modeling tool and direct synthesis method to enhance both robustness and efficiency. The preliminary results of AATC's industrial applications demonstrate its advantage in improving productivity at the early stage parametric design, especially for complex engineering systems.