共查询到18条相似文献,搜索用时 60 毫秒
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等通道转角挤压(Equal channel angular pressing,ECAP)方法是制备性能优异超细晶材料最常见的大塑性变形方法之一。模角、挤压路径、挤压道次、挤压温度和挤压速度等因素都会影响等通道转角挤压制备超细晶材料的性能;等通道转角挤压的模具也在不断地优化,如背压-等通道转角挤压(Back pressure ECAP,BP-ECAP)模具、可加热的模具以及在等通道转角挤压基础上形成的板材连续剪切技术等,这些新的模具可以改变ECAP变形过程中的组织均匀性。本文综述了等通道转角挤压制备超细晶材料的最新研究进展,并指出了几个需要深入研究的问题及方向。 相似文献
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研究了GCr15钢等通道转角挤压(ECAE)的原理与技术实施手段。通过设计ECAE模具的几何结构,研究了剪切应变累积效应的计算方法。通过对GCr15钢单道次ECAE加工后光学微观组织的观察,讨论了模具几何结构条件(转角与背转角大小)对GCr15钢微观组织变化的影响。结果表明:GCr15钢的ECAE变形组织形态较好地符合理论预测结果;多道次ECAE加工显著改善了GCr15钢的微观组织;通过ECAE工艺,也能够制备出大尺寸致密的细晶材料。 相似文献
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使用有限元方法模拟在等径通道挤压过程中,后压力对材料塑性变形的影响,并对多道次挤压试验结果进行分析比较.结果表明:施加后压力可以有效提高材料每道次挤压的塑性变形程度和分布均匀性.在多道次挤压过程中,施加后压力可以大幅度降低晶粒最终细化尺寸,降低挤压温度来减小温度对晶粒细化效果的影响. 相似文献
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A new technique to equal channel angular pressing of tubular samples has been proposed and investigated through experiments and simulations.Deformation behavior of copper tube sample was numerically analyzed during the first pass of tubular ECAP process.The investigation included the efect of various tube wall thicknesses on the efective strain magnitude and strain distribution uniformity.It is shown that tube wall thickness of 3.5 mm gives the optimum value for strain behavior.In addition,copper tube specimens with3.5 mm wall thickness have been successfully ECAPed up to four passes with the die channel angle of 90° using flexible polyurethane rubber pad.Micro-hardness measurements on both annealed and ECAPed tubes show that 33%and 57%increases in hardness value and also,50%and 70%reductions in the grain size were achieved after the first and fourth passes respectively.Furthermore,tube wall thickness measurements show that the process does not change the dimension of deformed specimens. 相似文献
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Majid Vaseghi Hyoung Seop Kim Ali Karimi Taheri Amir Momeni 《Journal of Materials Engineering and Performance》2013,22(6):1666-1671
In this study, the hardness inhomogeneity of billets during multi-passes of equal channel angular pressing (ECAP) at elevated temperatures is investigated and the effect of large strain deformation during ECAP on the hardness inhomogeneity characteristics due to dynamic aging of aluminum 6061 under a variety of temperatures and ram speed was studied by TEM and hardness measurements. The hardness results showed that the hardness distribution is more homogenous after four passes using the pressing route Bc. However, when the deformation temperature was considered, performing ECAP at 100 °C may provide the most homogeneous microstructure after multi-pressing as long as the total number of pressing passes is four. This indicates that a lower temperature (in the range of warm working) is favorable for achieving an ultrafine-grained/nanomaterial with a more homogenous microstructure. In order to quantify the inhomogeneity in the cross section of the as-pressed sample, an inhomogeneity index has been defined. The results show an increase in the hardness in the first pass with significant inhomogeneous deformation and a transition toward a more homogeneous structure with subsequent passes. 相似文献
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等径弯曲通道变形制备超细晶铜的力学行为 总被引:1,自引:0,他引:1
利用显微硬度计和电子拉伸机,研究了等径弯曲通道变形(Equal Channel Angular Pressing-ECAP)前后纯铜的硬度、力学性能,分析了ECAP制备超细晶铜(UFG)的强化机制。结果表明,纯铜在ECAP变形中出现了加工硬化-软化的饱和现象,即流动应力随变形量增加先迅速增大,在8道次达到最大(σb=410MPa),而后趋于饱和。强度可达400~410MPa,伸长率为12%~20%,硬度(HV)为140~146。利用MA模型合理解释了ECAP制备超细晶材料的拉伸力学行为。 相似文献
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等径角挤压法制备超细晶的研究现状 总被引:1,自引:11,他引:1
总结了等径角挤压(Equal Channel Angular Pressing,ECAP)过程中的影响因素、晶粒细化的机理等方面的研究进展,讨论了挤压温度、挤压速度在ECAP过程中对材料的影响,简述了ECAP的变形途径、变形次数对材料晶粒、材料变形量的影响。论述了由等径角挤压方法制备超细晶材料的发展现状并提出了一些需要进一步深入研究的方面。 相似文献
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对经过8道次等径角挤压的超细晶304不锈钢进行不同温度的退火处理,研究了退火温度对304不锈钢显微组织和力学性能的影响,并对断口形貌进行了观察。结果表明,304不锈钢的再结晶起始温度为650℃,而再结晶结束温度为900℃;在退火温度升高至750℃以上时,304不锈钢的组织为部分超细晶和发生再结晶的晶粒组成的双尺度结构;对8道次等径角挤压304不锈钢进行退火处理后,强度和屈强比降低,而断后伸长率提高,750℃退火30 min是较为适宜的退火工艺;随着退火温度升高,材料的断裂机制从脆性断裂逐渐转变为韧性断裂。 相似文献