工程金属材料的表面纳米化技术(一)

在表面机械处理方式下,材料表面可以通过强烈塑性变形而实现纳米化,获得表面为纳米晶、晶粒尺寸沿厚度方向逐渐增大的梯度结构。表面纳米4E（SNC）技术一方面能为研究形变诱发的纳米化过程和宽尺寸范围内（从微米到纳米量级）结构与性能的关系提供思路,制备理想样品;另一方面能通过纳米化显著地提高金属材料的性能,因此可望在工业上取得实际应用。文章从基本原理、制备技术、结构、性能和化学处理等方面介绍表面纳米化研究工作已取得的进展。     

工程金属材料的表面纳米化技术（二）

在表面机械处理方式下，材料表面可以通过强烈塑性变形而实现纳米化，获得表面为纳米晶、晶粒尺寸沿厚度方向逐渐增大的梯度结构。表面纳米化（SNC）技术一方面能为研究形变诱发的纳米化过程和宽尺寸范围内（从微米到纳米量级）结构与性能的关系提供思路，制备理想样品；另一方面能通过纳米化显著地提高金属材料的性能，因此可望在工业上取得实际应用。文章从基本原理、制备技术、结构、性能和化学处理等方面介绍表面纳米化研究工作已取得的进展。     

工业纯铁自纳米化组织的EBSD分析

运用高能喷丸技术实现了工业纯铁表面自纳米化,利用电子背散射衍射（ElectronBackscatteredDiffraction,EBSD）对自纳米化组织的结构特征进行了分析,在此基础上探讨了工业纯铁自纳米化机理。结果表明,工业纯铁自纳米化组织由三个典型区域组成,分别含有大量残存住错,大角度晶界及大量小角度晶界。自纳米化组织含有再结晶织构和形变织构,但由于晶粒取向差不同,变形难易程度不同导致两种织构的比例不同。位错运动、晶粒取向差不同导致变形不同步及发生再结晶是工业纯铁表面自纳米化过程中晶粒细化的主要原因。     

形变诱发纳米晶局域固态非晶化的研究进展

形变诱发纳米晶金属材料局域固态非晶化转变是近年来提出的获得局域固态非晶化组织的一种新途径,这种转变机制使得以位错、变形孪晶、晶界滑动和晶粒转动为主要变形机制的纳米晶材料中可能存在一种全新的塑性变形机制,并且,局域固态非晶化的临界转变条件和转变机制可为材料的结构优化设计提供依据。概括了国内外实验及数值模拟手段关于形变诱发局域固态非晶化转变的研究,例如采用机械球磨、高压扭转变形、经典力场和分子动力学等方法,证明了形变诱发局域固态非晶化转变的存在。此外,还分析了发生局域固态非晶化转变的内在机制。基于晶体相场模型的优势,提出用该方法模拟局域固态非晶化转变的突出之处,表明了晶体相场法能够有效研究局域固态非晶化转变过程。     

镁合金焊接接头表面自纳米化及其疲劳性能研究现状与展望

焊接接头表面纳米化解决了决定焊接接头疲劳裂纹萌生和扩展的内在因素之间的矛盾,在细化接头表面晶粒的同时,使基体保持粗晶状态,因而是提高焊接接头疲劳性能的一种有效方法。综述了镁合金表面自纳米化机理及研究现状,分析了表面自纳米化技术在改善镁合金焊接接头疲劳性能方面的研究概况,指出从镁合金焊接接头表面自纳米化的角度开展镁合金焊接接头疲劳性能改善研究具有重要意义。最后,对今后应用表面自纳米化技术改善镁合金焊接接头疲劳性能的研究方向做了展望。     

金属材料表面自纳米化及其研究现状

文章综述了材料表面自纳米化的国内外研究现状,包括表面自纳米化的制备方法、基本原理、表层结构及机理、性能研究,展望了表面自纳米化技术的发展前景及目前有待解决的问题。     

镁、铝合金表面自纳米化研究现状

综述了目前镁、铝合金表面自纳米化制备方法、性能、耐蚀性等方面的研究.材料经表面自纳米化后,表面纳米层有良好的热稳定性,表面硬度明显提高,不同的工艺对耐蚀性影响不同.提出了表面自纳米化技术研究还需解决的问题及趋势.     

金属材料表面自纳米化研究现状

综述了金属材料表面自纳米化技术的研究现状.表面机械加工自纳米化的原理是在一定的应力作用下,使金属材料表面层产生剧烈的塑性变形,导致晶粒细化.晶粒的细化机理主要取决于金属材料的晶格结构和层错能;表面自纳米化能显著提高金属材料的综合性能.展望了表面自纳米化技术的发展前景.     

镁铝纳米层状复合材料的简介

简单叙述镁基复合材料的研究现状,综述了层状金属复合材料的多种制备方法及其优缺点,并重点介绍复合轧制法来制备镁铝纳米层状复合材料。主要阐述镁铝复合相的表面自纳米化处理技术,特别是机械研磨技术的应用。展望了镁铝纳米层状复合材料的发展前景。     

金属材料表面自纳米化研究现状

综述了金属材料表面自纳米化技术的研究现状。表面机械加工自纳米化的原理是在一定的应力作用下，使金属材料表面层产生剧烈的塑性变形，导致晶粒细化。晶粒的细化机理主要取决于金属材料的晶格结构和层错能；表面自纳米化能显著提高金属材料的综合性能。展望了表面自纳米化技术的发展前景。     

非连续增强金属基复合材料剧烈塑性变形行为研究进展

综述了非连续增强金属基复合材料剧烈塑性变形(SPD)行为的研究进展,系统阐述了等径弯曲通道变形(ECAP)、高压扭转(HPT)、多向锻造(MF)、累积叠轧(ARB)和循环挤压压缩(CEC)5种SPD的加工原理和方法。集中介绍了这些方法在铝基、镁基、铜基和钛基等金属基复合材料方面应用的研究进展。重点介绍了金属基复合材料SPD的微观组织演化和变形力学行为,详细阐明了金属基复合材料SPD机制以及超细晶形成机理,指出了金属基复合材料在SPD中存在的深层次问题及发展趋势,展望了利用SPD方法制备超细晶非连续增强金属基复合材料的应用前景。     

Design and mechanical property analysis of ultrafine grained gears from AA5083 previously processed by equal channel angular pressing and isothermal forging

In this present study, the isothermal forging of two different gears is carried out from material previously deformed by the severe plastic deformation (SPD) process known as Equal Channel Angular Pressing (ECAP). At present, there are only a few studies which use this material predeformed that exhibits improved mechanical properties as a result of the SPD process for use in subsequent processes or applications. The design and optimization of the die geometry required for the isothermal forging of gears are shown and both microhardness and microstructure are compared when these forged gears are obtained from annealed material (N0) and ECAP-processed material (N2). With this present research work, it is demonstrated that there is an improvement in forgeability and microhardness as well as a decrease in the grain size of the material predeformed by SPD.     

脉冲加压镍原子在纳米晶铁中扩散行为研究

利用高能喷丸技术实现电工纯铁表面自纳米化,通过X射线衍射分析对表面变形层晶粒度进行表征;然后在Gleeble 1500型热模拟试验机上进行Ni的扩渗;利用扫描电子显微镜作能谱分析,对常规粗晶和纳米晶试样的扩散效果进行分析。结果表明,电工纯铁经喷丸处理,表面得到了纳米结构层;Ni在纳米晶中的扩散系数比同等条件下常规粗晶试样高1倍。     

The nanocrystalline structure formation in germanium subjected to severe plastic deformation

The peculiarities of nanocrystalline (NC) structure formation in germanium subjected to severe plastic deformation (SPD) are examined in this paper. Transmission electron microscopy (TEM), X-ray analysis and differential scanning calorimetry were employed in the structural study of germanium specimens. The crystal-to-amorphous transition induced by SPD in germanium is observed. The NC structure formation is the result of annealing at 850°C. Crystallites in the NC state have non-equilibrium grain boundaries (GB) and a particular “spread” diffraction contrast, observed by TEM, testifies to this.     

Repetitive Corrugation and Straightening of Sheet Metals

Recently, severe plastic deformation (SPD) techniques have been gaining wide popularity in developing nano/ultrafine grained (UFG) structured materials for a wide variety of applications. Among SPD techniques, there are a few techniques that are specially used to process metallic sheets and plates. Repetitive corrugation and straightening (RCS) is one such promising technique, which can produce fine grained structures in metallic sheets or plates in bulk. The process was introduced to develop UFG metallic sheets and plates nearly a decade ago and is now gaining great interest in the material processing field. The aim of the present review is to give a comprehensive summary of the state-of-the-art of the process in developing fine grained structured sheets. Emphasis has been given to discuss different material systems processed by RCS. The mechanism behind the grain refinement during RCS, promising applications, and future perspectives in developing UFG structured sheets or plates by RCS are also discussed.     

Modelling of equal channel angular pressing using a mesh-free method

Severe plastic deformation (SPD) processes are widely recognised as efficient techniques to produce bulk ultrafine-grained materials. As a complement to experiments, computational modelling is extensively used to understand the deformation mechanisms of grain refinement induced by large strain loading conditions. Although considerable research has been undertaken in the modelling of SPD processes, most of the studies have been accomplished using mesh-based methods, such as the finite element method (FEM). Mesh-based methods have inherent difficulties in modelling high-deformation processes because of the distortions in the mesh and the resultant inaccuracies and instabilities. As an alternative, a mesh-free method called smoothed particle hydrodynamics (SPH) is used. The effectiveness of this technique is highlighted for modelling of one of the most popular SPD techniques, equal channel angular pressing. A benchmark between SPH and FE calculation is performed. Furthermore, a number of simulations under different processing conditions are compared to existing literature data. A satisfactory agreement is found, which indicates that SPD processes can be approached by mesh-free methods, such as SPH.     

The new trends in fabrication of bulk nanostructured materials by SPD processing

During the past decade, fabrication of bulk nanostructured metals and alloys using severe plastic deformation (SPD) has been evolving as a rapidly advancing direction of nanomaterials science and technology aimed at developing materials with new mechanical and functional properties for advanced applications. The principle of these developments is based on grain refinement down to the nanoscale level via various SPD techniques. This paper is focused on investigation and development of new SPD processing routes enabling fabrication of fully dense bulk nanostructured metals and alloys with a grain size of 40–50 nm and smaller, namely, SPD-consolidation of powders, including nanostructured ones, as well as SPD-induced nanocrystallization of amorphous alloys. We also consider microstructural features of SPD-processed materials that are responsible for enhancement of their properties.     

Tribological properties of ultrafine-grained materials processed by severe plastic deformation

Processing by severe plastic deformation (SPD) has been developed extensively over the last two decades in order to produce ultrafine-grained (UFG) materials having submicrometre or nanometre grain sizes. An important material property for UFG materials is good wear resistance so that they may be used in a range of structural applications. An examination of the published data shows that only limited reports are available to date on the wear behaviour of SPD-processed materials and, furthermore, many of these results appear to be conflicting. The correlation of hardness and wear is limited because the wear property is a system property that in practice is influenced by a range of factors. Accordingly, this review is designed to examine recent reports related to the wear resistance of materials processed by SPD with particular emphasis on alloys processed using equal-channel angular pressing (ECAP), high-pressure torsion (HPT) and accumulative roll-bonding (ARB).     

Al-Cu合金纳米析出相回溶和再析出的研究现状及

综述了Al-Cu合金在强塑性变形过程中纳米析出相的演变规律,室温强塑性变形诱导Al-Cu合金析出相回溶,导致基体重新形成过饱和固溶体,继续对合金进行强塑性变形或时效处理,基体中析出再析出相,合金的力学性能显著提高。综合分析了析出相回溶的机理、机制及回溶和再析出对Al-Cu合金组织和性能的影响,阐述了Al-Cu合金纳米析出相回溶和再析出的研究方向和发展趋势,以期为制备性能优异的Al-Cu合金材料提供理论参考。     

Commercialization of Nanostructured Metals Produced by Severe Plastic Deformation Processing

The promise of nanotechnology is increasingly being realized as governments, universities, public and private research laboratories, and the various industrial sectors devote resources to this emerging area. Estimates for the economic impact of nanotechnology on existing global markets exceed 700 billion by the year 2008. Nanomaterials are projected to be one of the earliest components of nanotechnology to appear in commercial applications. Amongst the emerging new nanomaterials, bulk nanostructured metals produced by severe plastic deformation (SPD) have shown promise in a wide range of application areas. In this paper, we overview developments in severe plastic deformation technology, emphasizing progress since the international workshop “Investigations and Applications of Severe Plastic Deformation” held 2–8 August 1999 in Moscow, Russia. Then, we overview some of principal areas of application for SPD metals and alloys.