Mechanical properties of microconstituents in Nb-Si-Ti alloy by micropillar compression and nanoindentation

The micromechanical properties of both Nb solid solution (Nbss) and (Nb,Ti)3Si silicide in a ternary Nb-16Si-22Ti (in at%) alloy were evaluated by nanoindentation and micropillar compression techniques. Nanoindentation tests showed that (Nb,Ti)3Si possesses much higher hardness (15.6±0.6 GPa) and Young's modulus (253.3±8.4 GPa) than Nbss (5.2±0.4 GPa and 124.9±5.1 GPa, respectively). Stress-strain curves of each constituent were obtained by micropillar compression. The stress-strain behavior showed that (Nb,Ti)3Si exhibited a brittle fracture mode, while Nbss was able to bear large ductile deformation. The compressive failure strength of (Nb,Ti)3Si intermetallic and yield strength of Nbss were found to be 8.4±1.2 GPa and 0.9±0.1 GPa, respectively. The fracture toughness of the (Nb,Ti)3Si phase evaluated by cracks emanating from nanoindentation, was measured to be ~2.3 MPa-m1/2.