The effect of the specimen size on the mechanical characteristics of material, a phenomenon commonly referred to as the “size effect”, becomes increasingly important at micron and sub-micron dimensions of the specimen. However, the majority of size effect studies on face-centered cubic (fcc) metals have focused on pure elements, where deformation is accomplished by dislocation glide. In this work, single crystalline Ni – x at. % Co (with x = 0, 30, 50) solid solution micropillars were studied by mechanical testing and transmission electron microscopy (TEM) to elucidate the role of stacking fault energy on the size effect in Ni as a function of Co-addition. In situ strain rate jump (SRJ) microcompression testing allowed the evaluation of strain rate sensitivity and activation volumes for all pillar sizes at different strain rates, spanning over three orders of magnitude. TEM analysis showed that for an increase in Co content up to 50%, the SFE decreased from ~85 to ~28 mJ/m². We observed all Ni – x at. % Co micropillars to exhibit consistent size effect trends ($n=~-0.7$), independent of composition and yield criterion, and similar trends between activation volume and different sizes: activation volume increases with grain size/pillar size.

样品尺寸对材料机械特性的影响（通常称为“尺寸效应”的现象）在样品的微米和亚微米尺寸上变得越来越重要。但是，大多数关于面心立方（fcc）金属的尺寸效应研究都集中在纯元素上，其中通过位错滑行实现变形。在这项工作中，单晶Ni – x at。 通过机械测试和透射电子显微镜（TEM）研究了％Co（x分别为x，0、30、50）固溶微柱，以阐明堆垛层错能对Ni尺寸效应的影响（作为Co加成的函数）。原位应变率跳跃（SRJ）微压缩测试允许评估跨越三个数量级的不同应变率下所有支柱尺寸的应变率敏感性和激活体积。TEM分析表明，随着Co含量增加至50％，SFE从〜85降至〜28 mJ / m ²。我们观察到所有的Ni – x at。钴微柱表现出一致的尺寸效应趋势（$ñ=〜-0.7$），而与成分和产量标准无关，活化体积和不同尺寸之间的趋势相似：活化体积随晶粒尺寸/柱尺寸的增加而增加。