Incipient plasticity and deformation mechanisms in single-crystal Mg during spherical nanoindentation

Incipient plasticity in Mg single crystals was investigated using the pop-ins generated during spherical nanoindentation on (0 0 0 1), (1 0 −1 2) and (1 0 −1 0) surfaces. Representative deformed regions extracted from underneath indents by means of focused ion beam machining were examined by transmission electron microscopy (TEM) to identify the deformation mechanisms. Anisotropic elastic Hertzian contact theory was used to calculate indentation Schmid factors and the relevant resolved shear stresses at pop-in from the load-displacement curves. The pop-in statistics in conjunction with the TEM analysis showed that the most likely deformation mechanism responsible for pop-in is slip via 〈a〉 dislocations even in the case of indentation along the c-axis.