高压扭转致纯铜晶粒细化及与应变的关系

Grain refinement and its correlation with strain for pure copper subjected to high pressure torsion

设计并加工了在材料试验机上使用的高压扭转夹持装置,并用装置获得了不同扭转变形量的纯铜试样．使用电子背散射衍射技术测量了处理后试样品粒尺寸沿径向的分布．对比分析了晶粒细化程度和应变量的关系,提出了一个描述晶粒细化的简单剪切球模型．结果表明,晶粒细化程度随着应变量的增大而增强,平均晶粒尺寸为原始平均尺寸的1/50．当剪切应变小于10时,晶粒尺寸随着剪切应变的增大迅速变小;当剪切应变大于10时,晶粒尺寸的变化趋于缓慢,晶粒细化程度与Stuwe等效应变之间有幂函数关系．依据简单剪切球形晶粒的模型,得到了晶粒细化程度随剪切应变增大而增强的规律,并与实验数据的变化趋势一致．

A holding apparatus for high pressure torsion （HPT） treatment equipped with materials testing machine was designed and manufactured. Samples of pure copper were HPT treated by different counts of revolution i.e. experienced different extent of strain. Electron back scattered diffraction （EI3SD） was used to measure the grain size of HPT treated samples. The relationship between grain refinement and strain was analyzed and a model of simple shear sphere was proposed to account for grain refinement. The results revealed that grain refinement dramatically develops with increasing strain, with the average grain size down to one fiftieth of its original average size. The grain size decreases significantly when shear strain is less than 10, whereas when shear strain is larger than 10, the reduction of grain size is greatly decelerated. There is a power law relation between Stuwe equivalent strain and grain size variation. Based on the proposed model, the tendency of grain refinement as a function of increasing shear strain was obtained. The predicted grain size reduction with increasing strain from the model is in good agreement with experimental results.