中文摘要：

等通道转角挤压是制备块体超细晶材料的一种重要方法,模具通道内角是影响晶粒细化效果的关键要素。采用刚塑性有限元法对通道内角φ为锐角（60°≤φ≤90°）时的挤压过程进行分析,获得了试样在挤压过程金属的流动和变形规律。研究结果表明：在无摩擦的理想状况下,随φ减小,金属的流动趋于均匀,角部间隙减小,试样整体变形效果增强,当φ=60°时,角部间隙完全消失并形成变形死区;同时,接触摩擦和模具外圆角ψ对挤压效果的影响随φ减小而增强;采用适当大小的ψ不仅可以消除尖角锐角模具所产生的缺陷,提高金属流动和变形的均匀性,而且可显著降低所需的变形力。

英文摘要：

The equal channel angular extrusion （ECAE） is an important technology to produce the ultra-fine grained （UFG） materials. The deformation behavior of metal during the ECAE process with acute channel angle （60°≤φ≤ 90°） was investigated by rigid plastic finite element method. The results show that the die with acute channel angle can obtain more strain compared with the die with channel angle of 90°. Under optimal conditions with no friction, comer gap becomes smaller with the decrease of channel angle. When φ is 60°, corner gap completely disappears and deformation dead zone （DDZ） appears. The effect of contact friction on deformation behavior is more effective with the decrease of channel angle. Outer corner angle ψ has a great influence on extrusion effect of the metal with acute channel angle die. With a certain outer corner angle, not only the defects appear in a closed angle die can be eliminated, but also the deformation is more homogeneous and the load can be greatly reduced.