模具钢激光表面改性技术的研究进展

介绍了激光表面淬火、激光熔覆及激光表面合金化在模具钢表面改性技术方面的应用特点和研究现状,提出了实际应用中存在的问题及今后需深入研究的方向,为激光表面处理技术应用于模具钢的表面处理提供参考。     

钛及钛合金的激光表面改性研究现状

硬度低、耐磨性能差是制约钛合金发展的关键问题,而激光表面改性处理是解决这一问题的有效途径。结合近年来激光表面改性处理的研究进展,综述了激光表面处理的影响因素,激光表面处理表层的组织、性能及缺陷控制,并指出了目前存在的问题和今后研究的重点方向。     

钛合金表面激光改性技术研究进展

随着钛合金应用范围的不断扩大,对于钛合金的性能也有了更高的要求,因此钛合金的表面改性成为重要的研究热点,综述了激光合金化技术和激光熔覆技术在钛合金表面改性中的应用,并对其存在的问题以及发展趋势进行了分析总结。     

The science and technology of advanced structural ceramics

In recent years, the pace of developments in structural ceramics has accelerated, bringing both monolithic and composite materials closer to broad application. Although an improved scientific understanding of these materials has led to substantial advancements, their inherent brittleness remains a major challenge to use in demanding applications. There are several methods under study that may enable the materials’ properties to be mastered, but costs will have to be brought in line with competing materials to ensure widespread use.     

激光诱导表面改性制备铜基非晶-纳米晶粉末冶金摩擦材料

为改善铜基粉末冶金摩擦材料的摩擦磨损性能,研究了激光诱导表面改性制备铜基非晶-纳米晶粉末冶金摩擦材料方法.采用扫描电镜、透射电镜、X射线衍射仪及硬度计等对粉末冶金摩擦材料层微观组织及性能进行了表征,结果表明:由于激光的急速加热和冷却以及以小质点杂质形式分布于α-Cu基体中的Zn,Sn和Pb元素抑制了再结晶的形核及长大,导致铜基非晶一纳米晶粉末冶金摩擦材料的形成.同时激光表面改性处理后,α-Cu相的晶粒尺寸减小了35%,二类应变均方根值增大39%,位错密度增加97%.聚合生长状态的α-Cu产生边缘溶解,大体积α-Cu枝解细小化.摩擦材料表观硬度提高了12.7%,α-Cu相显微硬度提高了14%.耐磨性能提高45%,摩擦系数升高1%.     

The potential for advanced ceramics in automotive engine applications

Although the progress in industrial application of structural ceramics was over-forecast in the last decade, the materials appear to be on the cusp of application in certain automotive components. This article reports on a study of the economics of replacing certain metallic automobile valve-train components with ceramic components. Because of the costs of the materials and the associated processes, ceramic parts are most competitive in new designs and when used as valve-train systems.     

Fiber laser induced surface modification/manipulation of an ultrasonically consolidated metal matrix

Ultrasonic Consolidation (UC) is a manufacturing technique based on the ultrasonic joining of a sequence of metal foils. It has been shown to be a suitable method for fiber embedment into metal matrices. However, integration of high volume fractions of fibers requires a method for accurate positioning and secure placement to maintain fiber layouts within the matrices. This paper investigates the use of a fiber laser for microchannel creation in UC samples to allow such fiber layout patterns. A secondary goal, to possibly reduce plastic flow requirements in future embedding processes, is addressed by manipulating the melt generated by the laser to form a shoulder on either side of the channel. The authors studied the influence of laser power, traverse speed and assist gas pressure on the channel formation in aluminium alloy UC samples. It was found that multiple laser passes allowed accurate melt distribution and channel geometry in the micrometre range. An assist gas aided the manipulation of the melted material.     

人造金刚石表面的改性研究概况

综述了人造金刚石表面改性的3种主要方法:一是金刚石表面的金属化,如物理、化学气相沉积,化学镀、电镀、真空微蒸发镀、盐浴镀等,主要应用在金刚石工磨具和电子封装材料上;二是偶联剂或表面活性剂处理金刚石,以改善金刚石与有机体系的界面性能,在金刚石粉体分散和树脂磨具中应用;三是金刚石薄膜和纳米金刚石的功能化处理,在电化学、生物传感器、电极等材料上应用。为金刚石表面改性的研究和应用提供参考。      

Selective laser sintering: A qualitative and objective approach

This article presents an overview of selective laser sintering (SLS) work as reported in various journals and proceedings. Selective laser sintering was first done mainly on polymers and nylon to create prototypes for audio-visual help and fit-to-form tests. Gradually it was expanded to include metals and alloys to manufacture functional prototypes and develop rapid tooling. The growth gained momentum with the entry of commercial entities such as DTM Corporation and EOS GmbH Electro Optical Systems. Computational modeling has been used to understand the SLS process, optimize the process parameters, and enhance the efficiency of the sintering machine. For more information, contact Sanjay Kumar, Katholieke Universiteit Leuven, Department of Mechanical Engineering, Heverlee, Leuven, 3001, Belgium; +32 16 32 2534; fax 32 16 32 2987; e-mail sanjay.kumar@student.kuleuven.ac.be.     

陶瓷干法成型过程分析与建模

针对陶瓷千法成型过程机理复杂、影响因素众多的特点,从系统辨识和过程控制的角度,首先采用Hammerstein-Wiener(H-W)模型来描述一个完整的陶瓷干法压制成型过程,其次利用关键项分离技术和广义递推最小二乘法(RGIA)来估计模型参数。最后对陶瓷粉末压制成型过程进行仿真研究,建模结果验证了所提出建模方案的有效性。     

激光造型技术综述

对激光造型技术的优点、应用价值、加工机理等作了简单阐述,另外就该技术的发展历史和国外的研究状况作了具体介绍,之后对国内的研究情况作了归纳性介绍。根据目前激光造型技术的相关研究,提出激光造型技术今后的研究方向,并展望了未来的应用前景。     

Numerical modeling of advanced materials

The finite element (FE) method is widely used to numerically simulate forming processes. The accuracy of an FE analysis strongly depends on the extent to which a material model can represent the real material behavior. The use of new materials requires complex material models which are able to describe complex material behavior like strain path sensitivity and phase transformations. Different yield loci and hardening laws are presented in this article, together with experimental results showing this complex behavior. Recommendations on how to further improve the constitutive models are given. In the area of damage and fracture behavior, a non-local damage model is presented, which provides a better prediction of sheet failure than the conventional Forming Limit Diagram.     

Atoms to autos: A multi-scale approach to modeling aluminum deformation

A multi-scale, computational design approach for aluminum sheet alloys, which includes key inputs from the electronic, atomistic, microstructural, and continuum length scales, is reviewed within the context of room and elevated temperature forming. Specific examples, which are aimed at improving aluminum sheet materials for automobile components, include prediction of flow curves from tensile testing, forming limit diagrams, and component forming.     

A review of modeling and simulation of laser beam machining

Laser beam machining (LBM) is a widely used thermal advance machining process capable of high accuracy machining of almost any material with complex geometries. CO₂ and Nd:YAG lasers are mostly used for industrial purposes. Drilling, cutting, grooving, turning and milling are the applications of LBM with different material removal mechanisms. Modeling and simulation of the LBM process is indispensable for optimization purposes. Modeling can be done by implementing analytical, numerical, experimental and artificial intelligence-based methods. This paper provides a review of the various methods used for modeling and simulation of the laser beam machining process as well as key researches done in this field so far.     

A first-principles approach to modeling alloy phase equilibria

This paper presents a brief overview of recent developments in the application of first-principles calculations to the study of bulk and interfacial thermodynamic properties and phase equilibria in alloys. Among the applications discussed are calculations of: bulk thermodynamic properties, phase boundaries, interfacial free energies, and precipitate morphologies. The article concludes by highlighting some further recent developments that are likely to lead to increasing applications of these modeling techniques. For additional information, contact M. Asta, Northwestern University, Department of Materials Science and Engineering, 2225 North Campus Drive, Evanston, Illinois 60208-3108; telephone (847) 491-5940; fax (847) 491-7820; e-mail m-asta@northwestern.edu.