Size Dependent Compressive Strength of FIB Machined Single Crystal Manganese Pillars

The deformation behavior of single crystals of manganese pillars generated by focused ion beam (FIB), with diameters ranging from ~1 m to ~4.5 m, has been studied as a function of specimen size using micropillar compression at ambient temperature. The manganese pillars were machined from randomly chosen larger grains of polycrystalline metal. At ambient temperature, single crystals of manganese display chaotic slip planes emerging on the sample surface and brittle plastic deformation when the sample size is decreased to the micrometer scale. The manganese pillars reached very high flow stresses in the range of 4-5.6 GPa. The stress-strain curves of all tested manganese pillars demonstrated significant work hardening and smooth flow behavior, with strains up to 8-10%. After 10% strain, however, the flow stresses remained constant with no work hardening. As previously reported, the manganese pillars with undetermined orientation demonstrated a less pronounced size effect (-0.14) by the size effect exponent of BCC pillars.