试样高宽比对反复镦压影响的数值模拟与实验研究

Numerical and experimental investigation of the effect of height-width ratio of the sample on cyclic channel die compression process

摘要:

反复镦压可以在不改变试样形状和尺寸的情况下获得大变形。高宽比是影响反复镦压工艺的重要参数之一。本文采用有限元与实验验证相结合的方法研究了高宽比对纯铜试样镦压变形过程、微观组织及性能的影响。结果表明，镦压后的等效应变分布不均匀，高宽比越大，单道次镦压平均等效应变和等效应力都越高。1道次镦压后，晶粒被压扁，随高宽比增大，晶粒被压扁的程度越严重。3道次变形后形成了大量变形带，试样高宽比越大，变形带越窄。12道次镦压后，高宽比为2的试样晶粒更等轴、细小。镦压后纯铜的硬度明显提高，高宽比为2的试样镦压后硬度值更高。

Abstract:

Severe plastic deformation can be achieved in the sample via cyclic channel die compression (CCDC) without changing its shape and size. The height/width ratio is one of the important parameters that affect the CCDC process. A finite element method and experimental validation are employed to investigate the effect of height/width ratio of the sample on compression process, microstructure and properties in this study. The results show that the effective strain is inhomogeneous after deformation. The larger the height/width ratio is, the larger the average effective strain for a single pass compression, and the higher the effective stress. After one pass, grains are squashed, and more serious as the height/width ratio increases. After 3 passes, a large number of shear bands are formed, and become narrow with the increase of height/width ratio. After 12 passes, more equiaxed and finer grains are obtained in the sample with height/width ratio of 2. Hardness of pure copper increases significantly after CCDC, and the hardness value of the sample is higher with height/width ratio of 2.