椭圆截面螺旋等通道挤压剧烈塑性变形细晶化机理研究

项目名称： 椭圆截面螺旋等通道挤压剧烈塑性变形细晶化机理研究

项目编号： No.51275414

项目类型： 面上项目

立项/批准年度： 2013

项目学科： 机械、仪表工业

项目作者： 李付国

作者单位： 西北工业大学

项目金额： 80万元

中文摘要： 提出一种集周向扭转剪切、轴向挤压和径向镦粗变形为一体的椭圆截面螺旋等通道挤压（ECSEE）剧烈塑性变形（SPD）新方法。利用ECSEE工艺特殊的圆和椭圆截面的变换，通过有效组合挤扭变形方式，防止变形缺陷的过早产生，获得合适的背压和付应力及理想的SPD变形应力状态，实现切变形与正变形的合理时序与比例，满足SPD细晶化过程中对形变（应变）和流变（应变速率）机制的要求。并利用临界应变后，简单剪切所产生的平稳湍流，迅速模糊初始晶粒边界，快速实现应变硬化饱和及晶界旋转，最终获得具有大角度晶界的超细晶结构。SPD细晶机制与位错及晶界行为密切相关，而材料强度、塑性等的反常变化也与上述机制下的性能饱和密切关联，结合ECSEE工艺，分析不同晶体结构与层错能材料的多滑移、交滑移、单滑移、孪生和扭折等SPD细晶化机理，对于推动超细晶/纳米材料的SPD法制备和极限细化定量机理的研究具有重要的理论意义和学术价值。

中文关键词： 剧烈塑性变形；等通道螺旋挤压；工艺基础；晶粒细化；综合性能

英文摘要： A new severe plastic deformation (SPD) method named elliptical cross-section spiral equal-channel extrusion (ECSEE) is proposed. In order to prevent the embryo defective of deformation, to get the right back pressure, additional stress and the ideal SPD deformation stress state, to achieve reasonable sequence and proportion of normal deformation and shear deformation, and to meet the requirements of the mechanisms of deformation (strain) and rheology (strain rate) in the SPD refinement process, ECSEE technology integrates a set of circumferential torsion shear, axial extrusion and radial upsetting deformation, utilizes the conversion of round and ellipse cross-section, and effectively combines the shear and extrusion deformation. The ECSEE smooth turbulent generated by the simple shear after the critical strain, could rapidly blur initial grain boundaries, achieve saturation of strain hardening and rotation of grain boundaries, ultimately obtain the ultra-fine grain structure with high angle grain boundaries. The SPD refinement mechanism is closely related to dislocations and grain boundaries, and the abnormal relationship of strength-plasticity in materials is probably embroiled the saturated performance under the above-mentioned mechanism. Based on the combination characteristic of ECSEE technology, the SPD re

英文关键词： severe plastic deformation；equal-channel spiral extrusion；forming processes；grain refinement；comprehensive performance