Fracture mechanical testing of single crystal notched α-iron micro-cantilevers

Fracture mechanical testing of micro-sized cantilevers was conducted in order to quantify the fracture toughness and modes of fracture for the (1 0 0)[0 1¯ 1] and (1 0 1¯)[1 0 1] crack systems in α-iron. The testing was performed at both room temperature and at −75 °C. Previous molecular dynamics analysis has indicated brittle behavior for the (1 0 0)[0 1¯ 1] and ductile behavior for the (1 0 1¯)[1 0 1] orientation, giving rise to the question; could this be achieved with testing at the micro-level. Elastic-plastic fracture mechanics was applied due to the small sample size, rendering the cantilevers out of bounds in relation to linear-elastic fracture mechanics boundaries. Conditional fracture parameters, KQ and JQ, were determined through the load-displacement curves where the change in unloading stiffness was used to determine crack growth. The crack growth was corrected to fit micrograph measurements. By normalizing the JQ vs. crack growth curves with its critical values, a new characterization tool was deemed applicable and proved promising in characterizing fracture behavior.