摩擦力在ECAP成形时作用的有限元模拟

应用有限元方法对一种全新的可应用于板料的等通道角挤压(ECAP)方法中摩擦力的作用进行了有限元模拟.计算模拟结果表明,不同于常规的等通道角挤压中摩擦力的负面影响,在板料等通道角挤压方法中一定的摩擦力和尺寸精确的模具结构却是保证此类等通道角挤压正常进行的关键.     

等径角挤压变形奥氏体不锈钢的组织演变

 用实验方法研究了奥氏体不锈钢在等径角挤压冷变形(路径RC)过程中组织变化。实验结果表明：当剪切方向与孪晶带方向成一定角度时，在剪切力的作用下，孪晶逐渐由大块孪晶→由剪切带分割的孪晶(楼梯状)→小块状→奥氏体亚晶或马氏体晶粒；部分孪晶在剪切力作用下，剪切带可直接碎化成具有大角度位向差的细小晶粒(奥氏体亚晶+马氏体晶粒)，可发生马氏体相变；当剪切方向与孪晶带方向相同时，孪晶带区域也可发生马氏体转变；3道次变形后，具有明显特征的孪晶已很少，此后继续进行剪切变形，孪晶碎化组织(含马氏体)和奥氏体剪切滑移带(含碎化晶粒)的变形以剪切滑移方式进行，当奥氏体的滑移遇到阻力时，可局部形成局部形变孪晶来协调变形；随变形道次的增加，马氏体转变也越多，在多次剪切以及道次中的交叉滑移作用下，马氏体板条逐渐被高密度位错墙分割而碎化成细小的晶粒；8道次变形后，可获得60~230 nm的等轴晶粒。     

基于ECAP规则的可重构分层系统的设计与实现

给出了基于主动规则-ECAP（event-condition-action-parameter)规则的分层应用系统的框架和运行机制，用ECAP规则来描述应用程序的业务逻辑，完成过程组件的调用，通过修改ECAP规则和相关基本对象及其数据端口，有效而灵活地完成系统的重构，并以图书馆采访子系统为例，运用ECAP规则进行设计。     

ECAP铜基原位复合材料的组织与性能研究

室温下采用等通道变形(ECAP)制备了 Cu-5.7%Cr原位复合材料,研究了其力学性能,电导率以及原位纤维的演变.结果表明:经过ECAP后,第二相Cr发生了旋转和伸长,逐渐演变为细小的纤维,且纤维逐渐倾向于与x轴平行.Cu-5.7%Cr合金的硬度,抗拉强度在2道次前显著增加,延伸率则迅速下降.2道次以后,硬度和抗拉强度的增加缓慢,延伸率则保持在20%左右.随着变形道次的增加,电导率逐渐降低,4道次后趋于稳定,8道次后达到80%LACS.     

等径弯曲通道变形(ECAP)的研究现状及发展趋势

等径弯曲通道变形（equal channel angular processing,ECAP)是使材料经受强烈塑性变形的一种加工方法。本文介绍ECAP的国内外发展概况，对其方法和影响因素等做了概述，并对其应用前景做了进一步的展望。     

Improving hydrogen storage properties of magnesium based alloys by equal channel angular pressing

Equal channel angular pressing was applied to a commercial magnesium alloy ZK60 in order to improve its hydrogen storage properties. The microstructure refinement and increase in the density of crystal lattice defects caused by equal channel angular pressing increase hydrogen desorption pressure, change the slope of the pressure plateau in pressure-composition isotherms, decrease the pressure hysteresis, and accelerate the hydrogen desorption kinetics. It is argued that a proper design of the defect structure of materials is a key element in the search for economically viable and environmentally acceptable solutions for mobile hydrogen storage based on metal hydrides.     

Microstructure and mechanical properties of pure gold processed by equal channel angular pressing

The microstructure and mechanical properties of pure gold were examined after different number of equal channel angular pressing passes. The hardness and 0.2% proof stress from the compression tests were observed to increase only up to the fourth pass whereas the compressive strength at 40% strain kept increasing gradually with increasing the number of passes. Microstructure with low angle grain boundaries and shear bands were observed until the eighth pass and equiaxed grains with high angle grain boundaries were observed only after the twelfth pass.     

Effect of equal channel angular pressing (ECAP) on hydrogen storage properties of commercial magnesium alloy AZ61

Cast commercial AZ61 magnesium alloys were processed through equal channel angular pressing (ECAP) and were comminuted into chips by filing with a rasp in order to measure their hydrogen storage properties. The effects of the number of ECAP passes and the processing route of ECAP on the hydrogen storage properties of AZ61 magnesium alloys were investigated. ECAP processing led to severe dynamic recrystallization and grain refinement of the AZ61 alloys. Of the analyzed samples, the AZ61 alloy processed via the Bc ECAP route with eight passes exhibited the smallest grain size, the fastest hydrogen absorption and desorption rates, and the highest gravimetric hydrogen storage capacity of 6.2 wt%.     

强烈塑性变形法制备金属纳米晶体材料

通过分析变形特点,综述压制球磨粉末(SPDC)、等径角挤压(ECAP)和自身表面纳米化3种通过强烈塑性变形制备纳米晶体材料的原理与方法,分析强烈塑性变形的组织细化机制及所获得的纳米晶体材料的结构与性能特征,指出该研究领域所存在的问题和今后的发展方向。     

等通道转角挤压Al-26%Si合金的组织和冲击性能

采用等通道转角挤压工艺(ECAP)细化了Al-26%Si合金中的组织,研究了该合金在不同温度下的冲击性能及断口形貌。结果表明:ECAP能有效细化该合金的晶粒,块状初晶硅尺寸明显减小且棱角钝化,针状共晶硅呈颗粒状弥散分布于基体中,300℃下挤压16道次后合金的室温(11℃)冲击功约为铸态的5倍;低温下,挤压16道次后合金的冲击性能随温度下降变化不大;当冲击温度由室温升高至100℃时,合金的冲击性能有所下降;铸态试样的断裂机制以脆性断裂为主,挤压后试样的断裂机制以韧性断裂为主。