摘要：管材往复挤压是一种新的剧烈塑性变形技术，通过往复挤压可以获得具有超细晶粒的管材。本文通过数值模拟与实验研究方法探索管材往复挤压工艺。

模拟结果表明往复挤压模具芯棒凸台大小是影响往复挤压实验的关键因素，芯棒凸台越高，挤压管材变形量越大；芯棒凸台越长，挤压管材的变形量越大且内外壁部分产生变形不均匀分布，内壁变形大于外壁。通过管材往复挤压实验发现，凸台最小的芯棒往复挤压管材的成形质量最好，最高达到往复挤压11道次。经过往复挤压以后，纯铜管材组织明显细化，晶粒从退火态的400μm细化至亚微米级。管材的初始硬度为65HV，挤压1道次以后硬度立马上升到110HV。随后的往复挤压中硬度值上升较慢，11道次往复挤压硬度值达到135HV。管壁方向上硬度分布较为均匀，说明管材变形是均匀的。经过1道次挤压以后，管材的屈服强度由54.6MPa上升到286.7MPa，抗拉强度由198.9MPa上升到304.2MPa，管材的屈服强度和抗拉强度有了显著的提高。当经过往复挤压3道次以后，管材的屈服强度上升到348.4Mpa，抗拉强度上升到380.3MPa。

关键词：剧烈塑性变形；管材往复挤压；纯铜；模具设计

Abstract：Tube cyclic extrusion-compression is a new technique of severe plastic deformation, and the tube with ultrafine grain can be obtained by cyclic extrusion-compression. In this paper, through numerical simulation and experimental investigation methods, to explore the tube cyclic extrusion-compression process.

The simulation results show that the size of the mandrel boss is the key factor affecting the cyclic extrusion-compression experiment. The higher the mandrel boss is, the greater the deformation of the extruded tube is. The longer the mandrel boss is, the deformation of the extruded tube. The larger the inner and outer wall part of the deformation is uneven distribution, deformation of the inner wall is greater than the outer wall. Through the tube cyclic extrusion-compression experiments found that the minimum   mandrel  boss cyclic extrusion-compression tube forming the best    quality, up to 11 times the cyclic extrusion-compression. After repeated extrusion, the  pure copper tube is obviously refined, and the grains are refined from the 400 μm of the annealed state to the submicron level. The initial hardness of the tube is 65HV, and the hardness immediately rises to 110HV after 1 time. Subsequent cyclic extrusion-compression in the hardness value increased slowly, 11 times cyclic extrusion-compression hardness value of 135HV. Tube wall hardness distribution is more uniform, indicating that the tube deformation is uniform. After 1 time, the yield strength of the pipe increased from 54.6MPa to 286.7MPa, the tensile strength increased from 198.9MPa to 304.2MPa, and the yield strength and tensile strength of the pipe increased remarkably. When the cyclic extrusion-compression 3 times, the yield strength of the pipe rose to 348.4Mpa, tensile strength rose to 380.3MPa.

Keywords: Severe plastic deformation; Tube cyclic extrusion-compression; Pure copper; Die design

目 录

第一章 绪论 1

1.1选题的背景和意义 1

1.2往复挤压概述 1

1.3管材循环变形技术原理 2

1.3.1管材往复挤压（TCEC） 2

1.3.2管材循环扩口缩口（CFS） 3

1.3.3管材循环膨胀挤压（TCEE） 3

1.3.4管材通道角挤压工艺（TCAP）