ECAP道次对Q235钢拉伸性能及位错强化的影响

研究了ECAP道次对Q235钢拉伸性能与位错强化的影响。结果表明,ECAP加工明显提高了钢的强度,尤其是抗拉强度,但强度并非是随着ECAP道次的增加而增加。基于XRD分析和Taylor公式的定量计算,研究了ECAP提高强度的机理。结果说明,结构细化提高的强度小于位错密度增加提高的强度,后者对强度提供的贡献至少占到50%。     

等径转角挤压Cu-Cr-Zr合金的差热分析（英文）

对Cu-1Cr-0.1Zr合金在室温下进行16道次等径转角挤压(ECAP),挤压路径为B_c。利用差热分析研究合金中沉淀相的析出序列,计算每道次ECAP后合金储能、再结晶温度以及激活能。此外,对位错密度与电学性能之间的关系进行研究。结果表明:随着ECAP挤压道次的增加,合金中的储能增加,而再结晶温度则大幅度降低。     

等径角挤压模具对超细晶材料显微组织的影响

论述了等径角挤压（ECAP）制备超细晶材料工艺的研究进展，介绍了ECAP的技术原理和工艺特点，着重分析了ECAP模具对ECAP细晶材料的显微组织的影响．优化ECAP模具结构。     

等通道转角挤压7075铝合金动态再结晶组织晶粒度预报

采用等通道转角挤压(ECAP)对7075铝合金试样进行挤压,利用有限元软件对ECAP的连续动态再结晶组织晶粒度进行预报,采用有限元和实验相结合的方法,研究不同挤压道次对7075铝合金A路径ECAP过程组织晶粒度的影响。模拟结果表明,经过一道次、二道次和四道次A路径ECAP后试样中心区域的晶粒尺寸分别为24.8μm、20.2μm、16.7μm,晶粒随着挤压道次的增加不断细化。通过金相定量法计算可得一道次、二道次和四道次A路径ECAP实验后试样中心区域的晶粒度分别为26μm、20μm、16μm,与有限元预报结果吻合良好,最大误差小于5%,证明基于连续动态再结晶模型的有限元预报准确性较高。     

纯铝ECAP工艺研究

ECAP技术是一种基于大塑性变形技术的材料制备工艺．通过强烈塑性变形而获得亚微米甚至纳米级大尺寸块体材料．日益受到材料科学界的重视．被认为是制备超细晶材料最有应用前景的方法之一。本文利用有限元软件Deform-3D对ECAP变形过程进行数值模拟．分析试样宏观变形、微观组织性能的变化以及应变载荷的分布．同时进行ECAP挤压试验．对比分析ECAP变形过程．探寻ECAP试样变形机理。为ECAP应用于其他高性能材料和ECAP的进一步研究打下基础。     

600℃退火对等通道转角变形40Cr钢强度和位错强化的影响

研究了600℃退火对经完全退火预处理并经等通道转角挤压（ECAP）加工的40Cr钢强度和位错强化的影响。微观组织和拉伸试验结果表明,600℃退火使ECAP形变40Cr钢铁素体区发生再结晶,并使强度明显降低。经XRD分析和Taylor公式的定量计算说明,600℃退火对ECAP形变40Cr钢的位错强化影响很小,实际强度的降低不是来自于位错强化的降低,而是来自于其它强化机制（晶界亚晶界等）的减弱。     

等径角挤压力分析及实验研究

使用上限定理得到了等径角挤压(ECAP)过程中圆柱试样的上限挤压力解析式,并对纯铜圆柱试样进行了等径角挤压实验及有限元仿真模拟,结合实验与有限元模拟对ECAP过程的上限挤压力解析式进行了两方面的验证,结果显示解析式计算值、仿真模拟值和实验值三者结果相近,表明解析式具有一定的准确性。另外,使用ABAQUS有限元软件对不同半径及不同长度的纯铜圆柱试样ECAP过程进行了有限元模拟分析,并结合理论解析式,讨论了试样半径及试样长度对上限挤压力大小的影响。结果表明,圆柱形试样的半径和长度与ECAP挤压力正相关。但是,对于半径大于4 mm的试样,有限元模拟结果比解析式计算值大,而且随着半径的增大,差值有增大的趋势。     

模具结构对等径角挤压材料显微组织的影响

概述了等径角挤压（Equal ChannelAngular Pressing）制备超细晶材料工艺的研究进展；介绍了ECAP的技术原理和工艺特点；着重分析了ECAP模具对ECAP细晶材料的显微组织的影响，优化ECAP模具结构。     

200和400℃退火对ECAP形变40Cr钢拉伸性能与位错强化的影响

研究200和400℃退火对经完全退火预处理并等通道转角挤压(ECAP)加工的40Cr钢拉伸性能和位错强化的影响。拉伸试验表明,200和400℃退火对ECAP形变40Cr钢屈服强度没有明显影响,抗拉强度提高,应变硬化能力提高,但塑性降低。基于XRD分析和Taylor公式的定量计算说明,200和400℃退火对ECAP形变40Cr钢的位错强化影响较小,抗拉强度的提高和塑性的降低主要与材料内部退火导致的可运动位错数量减少等因素有关。     

等通道角挤压制备细晶ZK60镁合金的组织与力学性能

利用两种等通道角挤压(ECAP)方法(普通单步ECAP和两步ECAP)制备细晶ZK60合金。采用金相显微镜、扫描电镜、透射电镜和X射线衍射仪对合金的组织和织构进行观察,通过拉伸试验研究不同ECAP方法对合金力学性能的影响。结果表明:与单步ECAP变形相比,两步ECAP变形,由于降低了变形温度,晶粒细化效果更好;经过(240℃,4道次)+(180℃,4道次)两步ECAP变形后,合金晶粒细化至约0.8μm;合金的力学性能与材料的织构密切相关,由于存在织构软化效应,与挤压态相比,经单步ECAP变形后合金的强度有所降低,而伸长率明显提高;但经两步ECAP变形后,由于细晶强化和亚结构强化的作用,合金的强度得到提高。     

基于等径角挤压（ECAP）的超细晶铸造镁合金制备研究

研究了铸造镁合金等径角挤压（ECAP）的原理与技术实施手段.通过设计ECAP模具的几何结构,研究了剪切应变累积效应的度量方法.通过对AM60镁合金铸锭单道次ECAP加工后光学显微组织的观察,讨论了模具几何结构条件（转角与背转角大小）对变形组织演化形态的影响.根据多道次ECAP试验的位移-挤压力关系曲线,考察了加工工艺条件（加工道次数、背压与加工速率）对变形组织形态的影响规律.分析了镁合金ECAP加工技术的试验和模拟方案.研究表明：AM60镁合金铸锭的ECAP变形组织形态较好地符合理论预测结果;多道次ECAP加工显著改善了AM60镁铸锭的微观组织;对于具有粗大晶粒的铸造镁合金而言,ECAP工艺能以机械化冶金方式制备其超细晶结构.     

Consolidation of AA 7075-2 wt% ZrO_2 Composite Powders by Severe Plastic Deformation via ECAP

The powders of the AA 7075-ZrO_2 were mixed by mechanical milling, but it was found that the system presents a few disadvantages when processed by conventional sintering and hot extrusion, since intermetallic phases between ZrO_2 particles and alloying elements were formed. Equal channel angular pressing(ECAP) processing was proposed as an alternative method to consolidate the composite where there is no intermetallic formation. The analysis of the ECAP process showed that the intermediate temperature(220 ℃) produced a higher consolidation level than conventional sintering and hot extrusion(400 and 500 ℃, respectively). This fact was supported by relative density analysis. In the case of the sintered and hot-extruded sample, the relative density exhibited a value of 0.95, while ECAP sample showed a value of 0.98. Hardness values show that microstructural refinement obtained during mechanical milling was preserved during ECAP processing even when it was carried out at 220 ℃.     

高层错能7003铝合金ECAP晶粒细化位错机制研究

在室温对完全时效7003铝合金进行4道次ECAP(Bc)挤压,成功获得大约200nm至几百纳米的超细晶粒。借助透射电镜(TEM)观察ECAP变形过程中的微观组织特征,如位错缠绕区(DTZ)、位错胞结构、孤立位错胞(IDC)、稠密位错墙(DDW)、胞块(CB)、显微带(MB)和S带等。7003铝合金在变形过程中的细化机制主要是位错分割机制。     

等径角挤压法制备块体超细晶材料的研究现状及展望

对块体超细晶材料的研究是近年来的一大热点.大塑性变形法（Sever Plastic Deformation,SPD）之一的等径角挤压（Eaqual channel angular pressing ,ECAP）法,可以在室温或不太高的温度下,将材料的晶粒由几微米至几十微米细化至200nm～400nm,材料的性能得到提高,并且ECAP法有着相对简单的制备工艺及较好的细化效果.本文介绍了ECAP处理对提高材料的强度、疲劳寿命、超塑性等的贡献以及影响ECAP工艺的因素,分析了ECAP目前存在的问题,并对ECAP的应用前景进行了展望.     

Microstructure evolution and mechanical behavior of AZ31 Mg alloy processed by equal-channel angular pressing

AZ31 Mg alloy bar was subjected to 8-pass equal-channel angular pressing(ECAP) at 623 K. Microstructure evolution was observed by optical microscopy(OM) on cross section and X-ray diffraction analysis. The room temperature mechanical properties of the ECAP processed specimens were also investigated. A fine-grained structure with an average sub-grain size of 9 μm is obtained after 7 ECAP passes. XRD analysis indicates that after ECAP, in placing of planes and become the dominant directions that are favourable for grain refinement. ECAP processed AZ31 Mg alloy exhibits significant improvement in elongation but decrease in strength. The elongation of the specimen increases continuously up to 2 passes and then remains stable at further passes. This improvement can be related to the evolution of crystallographic texture and the scattered orientation of the basal plane (0001).     

室温等径转角挤压对18Ni(C-250)马氏体时效钢微观组织和拉伸性能的影响

采用等径转角挤压（ECAP）工艺在室温下对18Ni（C-250）马氏体时效钢进行单道次冷变形.对比固溶处理试样480℃时效曲线、固溶+ECAP处理试样的460和480℃时效曲线发现,一道次ECAP变形及随后的时效处理能够使马氏体时效钢的峰值时效时间明显缩短,峰值强度提高约100 MPa.结构分析表明,ECAP态实验钢的马氏体板条宽度为100—200 nm,随后的时效过程对马氏体板条宽度影响不大,而ECAP工艺对棒状δ-Ni3Mo相析出尺寸有显著影响.统计结果表明,经4 h时效处理后.固溶+480℃时效态、固溶+ECAP+480℃,460℃时效态的δ-Ni₃Mo宽度（直径）分别为4.92,12.33和3.54 nm.此外,ECAP工艺还促使18Ni马氏体钢中δ-Ni3Mo相在时效后期加速分解,使强度迅速衰减.     

Using equal-channel angular pressing for the production of superplastic aluminum and magnesium alloys

Equal-channel angular pressing (ECAP) is a useful tool for achieving exceptional grain refinement in bulk metallic alloys. Typically, the grain sizes produced through ECAP are in the submicrometer range, and thus they are smaller by up to an order of magnitude than the grain sizes attained through typical thermomechanical treatments. As a consequence of these ultrafine grains, the as-pressed alloys may exhibit superplastic ductilities at faster strain rates than in conventional superplastic alloys. This work initially describes the application of ECAP to two different alloys. First, results are presented for a commercial Al-2024 alloy where this alloy was selected because it contains no minor additions of either zirconium or scandium to assist in restricting grain growth. The results show that superplasticity is achieved through the use of ECAP. Second, results are described for a Mg-0.6%Zr alloy where this alloy was selected because it is the optimum composition for achieving a high damping capacity. Again, processing by ECAP produces superplastic ductilities not attained in the cast alloy. The second part of this work demonstrates that processing by ECAP may be extended from conventional rod or bar samples to samples in the form of plates. This is a very attractive feature for industrial superplastic forming applications. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

等通道转角挤压法制备超细晶纯钛的研究进展

近年来,围绕超细晶纯钛的制备及其性能提升方面开展了许多研究。本文综述了制备超细晶纯钛块材的等通道转角挤压工艺及其重要参数,分析了挤压过程中纯钛的位错滑移及孪晶变形机制。超细晶纯钛的强度、塑性、抗疲劳性能显著提高,而耐蚀性测试结果呈多样性,有待进一步研究。等通道转角挤压和后续热机械处理的结合,可进一步提高超细晶纯钛的综合性能,表明采用ECAP技术制备的超细晶纯钛在各行各业有着广阔的发展前景。     

Correlation between microstructure and mechanical properties of severely deformed metals

There is a correlation between the microstructure and the mechanical behavior of ultrafine-grained face centered cubic (fcc) metals processed by equal-channel angular pressing (ECAP). It is shown that the saturation yield strength is related to the maximum dislocation density according to the Taylor equation and, in addition, the value of the parameter α in the Taylor equation is strongly affected by the stacking fault energy because of different geometrical arrangements of dislocations within the grains. It is also demonstrated that the ductility of Cu processed by ECAP decreases with increasing strain but at extremely high strains the ductility is partially restored due to the recovery of the microstructure.     

等通道转角挤压制备超细晶材料的最新研究进展

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。