共查询到18条相似文献,搜索用时 171 毫秒
1.
2.
等径角挤压(ECAP)是一种以纯剪切方式实现块体材料大塑性变形从而获得超细晶材料的工艺。介绍了ECAP工艺的技术原理、工艺路线、研究现状及该工艺存在的优缺点。阐述了目前基于传统ECAP工艺的改进工艺的研究状况,包括ECAP模具的改进以及传统ECAP工艺与其他工艺的合成两个方面的内容,并预期了今后ECAP工艺的发展方向。 相似文献
3.
4.
5.
6.
7.
8.
9.
等通道转角挤压工艺(Equal Channel Angular Pressing,ECAP)是通过剧烈塑性变形改变微观组织结构生产超细晶粒材料的材料加工方法,工件变形的均匀性一直是ECAP 工艺过程中影响材料性能的主要原因之一.采用空间转换法实现了AZ31镁合金多道次ECAP挤压过程中有限元分析相关场量的准确传递,完成了四种不同挤压路径ECAP多道次挤压工艺的有限元模拟,获得了相应挤压件累积等效应变的分布规律.研究确定了经过四道次ECAP挤压以后等效应变累积最为均匀的挤压路径.通过微观组织观察和室温拉伸力学性能实验探讨了不同路径多道次ECAP挤压AZ31镁合金的组织性能变化规律.分析结果表明通过合适的变形路径可以获得细小而均匀的微观组织,当材料的应变累积均匀时,其力学性能也较好. 相似文献
10.
本研究通过等径通道挤压(ECAP)对孪晶诱导塑性变形钢(TWIP钢)在300℃下进行了晶粒细化,并运用金相显微镜、电子背散射衍射(EBSD)、透射电镜(TEM)观察了经不同道次挤压后TWIP钢的晶粒、孪晶形貌及位错组织。结果表明,在均匀化退火状态下,试样晶粒基本呈现等轴状态,通过测微尺测量晶粒尺寸,约为(90±30)μm。在1道次挤压后,晶粒沿剪切方向显著伸长,并有尺寸较小的新晶粒产生,许多形变孪晶在剪切带中产生。2道次挤压后新产生的细小晶粒增多,并开始产生许多微孪晶,孪晶易于在晶界处产生。经过4道次等径通道挤压,晶粒逐渐细化至超细晶状态,晶粒尺寸达到0.3~1μm,孪晶厚度随挤压道次的增多而不断减小,甚至达到几十纳米。在不同晶粒尺寸下,TWIP钢在高温ECAP过程中产生孪晶的机理不同。 相似文献
11.
Local severe plastic deformation for producing ultrafine‐grained regions The methods of severe plastic deformation are able to produce semi‐finished products with a homogenous ultrafine‐grained microstructure. An alternative option is the formation of ultrafine‐grained layers or rather a gradation of the grain size. The qualification of incremental bulk forming processes is concluded from an analysis of methods for producing ultra fine‐grained materials and the kneading in cyclic forming. Spin extrusion is investigated regarding the formation of ultra fine‐grained regions. Tests are carried out to analyse the grain refinement in cyclically deformed regions. 相似文献
12.
Dan Liu Daoxin Liu Junfeng Cui Xingchen Xu Kaifa Fan Amin Ma Yuting He Sara Bagherifard 《材料科学技术学报》2021,84(25):105-115
Severe plastic deformation is known to induce grain refinement and gradient structure on metals'sur-faces and improve their mechanical properties.However,the fundamental mechanisms behind the grain refinement and micromechanical properties of materials subjected to severe plastic deformation are not still well studied.Here,ultrasonic surface rolling process(USRP)was used to create a gradient microstructure,consisting of amorphous,equiaxed nano-grained,nano-laminated,ultrafine laminated and ultrafine grained structure on the surface of TB8 β titanium alloy.High energy and strain drove element co-segregation on sample surface leading to an amorphous structure during USRP processing.In situ transmission electron microscope compression tests were performed in the submicron sized pillar extracted from gradient structure and coarse grain,in order to reveal the micromechanics behavior of different grain morphologies.The ultrafine grained layer exhibited the lowest yield stress in comparison with single crystal and amorphous-nanocrystalline layers;the ultrafine grained layer and single crystal had an excellent strain hardening rate.The discrepancy among the grain sizes and activated dislocation sources led to the above mentioned different properties.Dislocation activities were observed in both compression test and microstructure evolution of USRP-treated TB8 alloy.An evolution of dislocation tangles and dislocation walls into low angle grain boundaries and subsequent high angle grain bound-aries caused the grain refinement,where twinning could not be found and no phase transformation occurred. 相似文献
13.
X. Ma R. Lapovok C. Gu A. Molotnikov Y. Estrin E. V. Pereloma C. H. J. Davies P. D. Hodgson 《Journal of Materials Science》2009,44(14):3807-3812
Ultrafine grained materials produced by severe plastic deformation methods possess attractive mechanical properties such as
high strength compared with traditional coarse grained counterparts and reasonable ductility. Between existing severe plastic
deformation methods the Equal Channel Angular Pressing is the most promising for future industrial applications and can produce
a variety of ultrafine grained microstructures in materials depending on route, temperature and number of passes during processing.
Driven by a rising trend of miniaturisation of parts these materials are promising candidates for microforming processes.
Considering that bi-axial deformation of sheet (foil) is the major operation in microforming, the investigation of the influence
of the number of ECAP passes on the bi-axial ductility in micro deep drawing test has been examined by experiments and FE
simulation in this study. The experiments have showed that high force was required for drawing of the samples processed by
ECAP compare to coarse grained materials. The limit drawing ratio of ultrafine grained samples was in the range of 1.9–2.0
with ECAP pass number changing from 1 to 16, while a higher value of 2.2 was obtained for coarse grained copper. However,
the notable decrease in tensile ductility with increase in strength was not as pronounced for bi-axial ductility. The FE simulation
using standard isotropic hardening model and von Mises yielding criterion confirmed these findings. 相似文献
14.
A new technique for producing ultrafine grained materials by severe plastic deformation is proposed. The principle and possible design of this technique, referred to as “cone–cone method,” are outlined and the first results of numerical simulations that demonstrate its feasibility are reported. These results give promise with regard to achieving very large plastic strains and the concomitant grain refinement in sheet products. 相似文献
15.
Microstructural change of ultrafine-grained aluminum during high-speed plastic deformation 总被引:5,自引:0,他引:5
N. Tsuji T. Toyoda Y. Minamino Y. Koizumi T. Yamane M. Komatsu M. Kiritani 《Materials Science and Engineering: A》2003,350(1-2):108-116
Effect of strain rate on microstructural change in deformation of the ultrafine grained (UFG) aluminum produced by severe plastic deformation (SPD) was studied. Commercial purity 1100 aluminum sheets were highly strained up to an equivalent strain of 4.8 by the Accumulative Roll-Bonding (ARB) process at ambient temperature. The ARB-processed sheets were found to be filled with pancake-shaped ultrafine grains surrounded by high-angle grain boundaries. The ultrafine grains had a mean grain thickness of 200 nm and a mean grain length of 1100 nm. The ultrafine-grained aluminum sheets were deformed at various strain rates ranging from 2 to 6.0×104 s−1 by conventional rolling, ultra-high-speed rolling, and impact compression. High-speed plastic deformation generates a large amount of heat, inducing coarsening of the ultrafine grains during and after deformation. On the other hand, it was also suggested that high-speed plastic deformation is effective for grain-subdivision, in other words, ultra-grain refinement, if the effect of heat generation is extracted. 相似文献
16.
Jizhong Li Wei XuXiaolin Wu Hua DingKenong Xia 《Materials Science and Engineering: A》2011,528(18):5993-5998
Ultrafine-grained pure magnesium with an average grain size of 0.8 μm was produced by refining coarse-grained (980 μm) ingot by multi-pass equal channel angular pressing (ECAP) at room temperature with the application of a back pressure. The compressive deformation behaviour at room temperature depended on grain size, with deformation twinning and associated work hardening observed in coarse-grained Mg, but absent in the ultrafine grained material as decreasing grain size raised the stress for twinning above that for dislocation slip. The ultrafine grained Mg showed good plasticity with prolonged constant stress after some initial strain hardening. 相似文献
17.
B. Ratna Sunil 《Materials and Manufacturing Processes》2015,30(10):1262-1271
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. 相似文献
18.
Andreas Böhner Verena Maier Karsten Durst Heinz Werner Höppel Mathias Göken 《Advanced Engineering Materials》2011,13(4):251-255
Several processes of severe plastic deformation are suitable for the production of materials with ultrafine‐grained microstructures which are known to exhibit high strength and often good ductility as well as strain rate sensitive behavior. The most promising ones are equal channel angular pressing (ECAP) for bulk material and accumulative roll bonding (ARB) for the production of sheet material. In order to evaluate the influence of the process on these mechanical properties and the strain rate sensitivity, tensile tests, and nanoindentation tests were performed on material produced up to similar effective plastic strains of εARB = 6.4 and εECAP = 6.3. It could be shown that the macroscopic strength is slightly higher for ARB than for ECAP material and vice versa in nanoindentation. Independent of the testing method, the strain rate sensitivities and activation volumes are similar for both materials. Thus, both processes performed up to similar effective plastic strains lead to comparable improvements in the mechanical properties. Additionally it could be shown, that this comparison allows the identification of the dominant deformation mechanism which is responsible for the observed strain rate sensitivity. 相似文献