In-situ transmission electron microscopy investigation of compressive deformation in interphase-precipitated carbide-strengthened α-iron single-crystal nanopillars

Compressive deformation tests were carried out during in-situ transmission electron microscopy to investigate the deformation behaviors of alpha-iron nanopillars with or without interphase-precipitated carbides. Three kinds of alpha-iron nanopillars were prepared from titanium-molybdenum-free and titanium-molybdenum-containing steels: one interphase-precipitated carbide-free and two interphase-precipitated carbide-bearing pillars with carbides of different sizes (4.7 nm and 3.0 nm after holding at 700 degrees C and 650 degrees C, respectively) and different number densities. In-situ observation provided direct evidence that interphase-precipitated nanometer-sized carbides confined the movement of the dislocations, resulting in smaller strain bursts with a significantly higher strength, in contrast to the behaviors of the pillars without carbides. The individual strain bursts in the in-situ stress-strain curves, which were associated with the corresponding dislocation substructures in the three kinds of pillars, are discussed.