Effect of diamondoids on the microstructure and mechanical behavior of nanostructured Mg-matrix nanocomposites

Nanostructured Mg-10Al nanocomposites reinforced by diamondoids were processed via cryomilling and spark plasma sintering. The effect of 1 wt% of diamantane on the microstructure of the nanostructured Mg-10Al nanocomposites was studied using scanning and transmission electron microscopies, electron dispersive spectroscopy and X-ray diffraction. A detailed microstructural examination revealed that diamondoids mainly located within the Mg-matrix induce a lattice strain along the c-direction and a potential effect on the γ-Al12Mg17 precipitation. The mechanical behavior of the nanostructured Mg-based nanocomposites was investigated by micro- and macro-compression tests along with in-situ SEM nanoindentation experiments at room temperature. The compressive strength, elastic modulus and hardness of the nanocomposites were found to be significantly improved as compared with the mechanical behavior of diamondoids-free nanostructured Mg-10Al alloys. Since no change in the grain size has been found after adding diamantane, we attribute the enhanced mechanical behavior of the nanocomposites to a combined effect of precipitation hardening and the microscopic residual stress generated by diamantane-Mg matrix mismatch. Our results provide new insights into the mechanisms involved in the development of high-performance Mg-nanocomposites.