In-situ transmission electron microscopy investigation of the deformation mechanism in CoCrNi and CoCrNiSi0.3 nanopillars

CoCrNi and CoCrNiSi_0.3 nanopillars exhibited distinct deformation behaviors under in-situ compression experiments with a strain rate of 2 × 10^–3 s^-1 in a transmission electron microscope. The former was mainly deformed through slip-dislocations and the formation of slip-bands with edges extending to the nanopillar's boundaries; in contrast, the latter was primarily deformed by twinning and partitioned by deformation nanotwins, with different variants intersecting each other to form closed nano-blocks. Si addition not only enhanced the solid solution strengthening effect but also facilitated the formation of nanotwins, resulting in a delayed first strain burst in the CoCrNiSi_0.3 nanopillar at a strain of 9.6 % with strength 39 % higher than that in CoCrNi at a strain of 7.1 % during the in-situ deformation. In addition, closed nano-blocks effectively strengthened the CoCrNiSi_0.3 nanopillar, which possessed strength 24 % higher than that of the CoCrNi nanopillar at the same strain of ∼20 %.