样品尺寸对Pd基块体非晶合金内部剪切带的影响

Effect of Specimen Size on Internal Shear Bands in Pd-based Bulk Metallic Glasses

摘要:

以Pd79Cu4Au2Si10P5块体非晶合金为对象，研究了不同尺寸合金的塑性变形行为及其内部剪切带特征。结果表明，直径为1, 2和3 mm的该非晶合金都具有良好的塑性变形能力，其塑性变形量随着试样尺寸的增大而降低，分别约为13%, 10%, 8%。不同尺寸试样的应力-应变曲线有明显不同的锯齿流变，2 mm试样锯齿振幅最大，3 mm试样锯齿振幅最小，而且1和3 mm试样的应力-应变曲线的锯齿间隔都比2 mm试样的小。金相显微镜的观察结果表明，随着试样尺寸的增加，其内部主剪切带密度降低，次生剪切带密度增加。在扫描电镜下能明显看到内部主剪切带厚度随着试样尺寸的增加而增加

Abstract:

Plastic deformation behavior and the features of internal shear bands in Pd79Cu4Au2Si10P5 bulk metallic glasses were investigated. The results show that the samples with diameters of 1 mm, 2 mm and 3 mm all have lager plastic deformation and the plastic strain is about 13%, 10% and 8%, respectively. In addition, the samples with different diameters have distinctly different serrated flows on the engineering stress-strain curves. The serrated-flow amplitude of the specimen with diameter of 2 mm is the largest, and the smallest serrated-flow amplitude is obtained in the specimen with diameter of 3 mm. The serrated-flow space of the specimens with diameters of 1 and 3 mm is smaller than that of the specimen with diameter of 2 mm. The results observed by optical microscopy show that, with the increase of sample size, the density of the internal primary shear bands decreases, but the density of the secondary shear bands increases. Further studies by scanning electron microscopy show that the thickness of primary shear band increases with the increase of sample size