EBSP study of the annealing behavior of aluminum deformed by equal channel angular processing

Commercial purity aluminum (99.5%) was fabricated by equal channel angular pressing (ECAP) up to total accumulated strains of approx. 10. The annealing behavior of material deformed to total strains of approx. 1 and 10 was investigated, using heat treatments of 2 h at various temperatures from 100 to 500 °C. The microstructure of the annealed materials was characterized using the electron back-scatter pattern technique. A number of parameters were determined including the distribution and average values of both the boundary spacings and misorientations. For samples deformed to a total strain of 1, annealing resulted in discontinuous recrystallization. For samples deformed to a total strain of 10, annealing resulted in microstructures exhibiting characteristics of both uniform coarsening and, in a number of places, of discontinuous recrystallization. An attempt was made, based on the boundary spacing distributions, to separate these two components. The grain size after annealing was still however small, being just 6.4 μm after 2 h at 300 °C.     

ECAP制备的亚微米7050铝合金的力学性能和微观结构

采用等通道角挤压法 (ECAP法 )制备亚微米 70 5 0铝合金。为了提高合金的力学性能 ,在挤压过程中增加了固溶时效处理工艺 ,并对 70 5 0铝合金在不同处理工艺条件下的显微组织和力学性能的变化进行了研究。结果表明 :ECAP挤压后进行固溶和时效处理能明显提高合金的力学性能。退火态合金经过ECAP后 ,晶粒尺寸明显细化到亚微米级。将挤压一次的试样进行固溶处理和时效处理 ,合金的强度在 5 75MPa左右 ,而延伸率能达到2 5 .5 %左右 ;若经等通道角挤压过的试样在固溶处理后立即进行再次挤压 ,并配合时效处理 ,合金强度能迅速达到 6 16MPa ,延伸率为 16 .9%。     

Monte-carlo modeling of grain growth in Zr equal channel angular pressed and recrystallized

Grain boundary character distribution in equal-channel-angular pressed Zr was studied. Using a die design of 90°/20° and an operation temperature of 350°C. The initial grain size of 20 μm was reduced to about 270 nm with 4 passes via route B_c. The grain growth kinetics of the recrystallized state was obtained by experiment and Monte-Carlo computer simulation, respectively, which showed good agreement. Based on kinetics and morphological characteristics, it was concluded that the grain coarsening mechanism was governed by normal grain growth. No sign of abnormal grain growth was detected either in the experiment or in simulation despite taking into consideration anisotropy in grain boundary energy as well as its mobility. This indicates that grain boundaries produced by severely deformed Zr are stable against explosive coarsening. The evolution characteristics of the microstructure in the present ECA pressed and recrystallized Zr differed from those of cold rolled Ti in that the grain boundary misorientation distribution and texture were rather stable during grain growth. Jointly Appointed by the Center for Advanced Aerospace Materials This article is based on a presentation made in the 2002 Korea-US symposium on the “Phase Transformations of Nano-Materials,” organized as a special program of the 2002 Annual Meeting of the Korean Institute of Metals and Materials, held at Yonsei University, Seoul, Korea on October 25–26, 2002.     

等径角挤压法制备超细晶的研究现状

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。     

两种塑性变形加工1060纯铝的组织和性能研究

采用等通道角挤压变形和累积叠轧焊两种大塑性变形方法对1060纯铝进行了加工，研究分析了纯铝在加工后的微观组织和力学性能变化和规律。结果表明：在相同的累积变形条件下，ARB和ECAP都能实现材料的晶粒细化和力学性能改善的目的。但南于两种塑性加工方式细化晶粒的机理和加工工艺不同．所以晶粒细化程度和力学性能的改善程度有所差别。ARB法将晶粒最小可以细化到500nm左右，ECAP法能细化晶粒到大小约为1μm。     

退火温度对等通道转角挤压态铁基形状记忆合金力学性能的影响

研究了退火温度对等通道转角挤压(ECAP)Fe17.80Mn4.73Si7.80Cr4.12N i合金力学性能及显微组织的影响。结果表明,等通道挤压工艺能显著提高合金的屈服强度和抗拉强度,两道次挤压后合金的屈服强度达到880 MPa,比固溶态高660 MPa。退火温度从300℃升高到600℃时,合金屈服强度和抗拉强度降低,伸长率升高。挤压后经700℃×30 m in退火后,材料的伸长率达到40%,屈服强度达到426 MPa,再结晶基本完成,晶粒尺寸仅为0.3~2.5μm。细晶强化是该合金强度和伸长率提高的主要原因。     

常规固溶态2024铝合金ECAP加工后的拉伸性能

在室温下对处于常规固溶处理态的2024高强铝合金成功实现了等效应变为0.5的等通道转角挤压(ECAP),将形变强化、时效强化和结构细化强化三者有机组合,制备出超高强铝合金,其硬度、屈服强度、伸长率分别高达1770MPa,550 MPa和14%.研究结果首次证明,固溶处理+室温ECAP+时效是提升常规高强铝合金的强度、制取超高强铝合金的一条有效途径.     

ECAP法制备超细晶铜的再结晶行为研究

在室温下，采用ECAP技术对纯铜进行了1-10道次的挤压，使其组织大大细化，得到了均匀、细小的等轴晶，平均晶粒尺寸为0．75μm。通过对不同ECAP道次后的退火试样的硬度测量和观察组织，结果表明：随ECAP道次的增加．开始再结晶的温度降低，再结晶软化的速率增加，ECAP8道次试样在433K发生静态再结晶。     

Controlling Corrosion Resistance of a Biodegradable Mg–Y–Zn Alloy with LPSO Phases via Multi-pass ECAP Process

Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y_1 Zn_(0.5) alloys with 18 R LPSO structure after equal channel angular pressing(ECAP). The results showed that the ECAP process changed the grain size and the distribution of LPSO particles thus controlled the total corrosion rates of Mg 98.5 Y_1 Zn_(0.5) alloys. During the ECAP process from 0 p to 12 p, the grain size reduced from 160–180 μm(as-cast) to 6–8 μm(12 p). The LPSO structures became kinked(4 p), then started to be broken into smaller pieces(8 p), and at last comminuted to fine particles and redistributed uniformly inside the matrix(12 p). The improvement in the corrosion resistance for ECAP samples was obtained from 0 p to 8 p, with the corrosion rate reduced from 3.24 mm/year(0 p) to 2.35 mm/year(8 p) in simulated body fluid, and the 12 p ECAP alloy exhibited the highest corrosion rate of 4.54 mm/year.     

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。