Internal friction in microcrystalline and nanocrystalline Mg

Strain amplitude dependence of the logarithmic decrement was measured on microcrystalline and nanocrystalline magnesium unreinforced and reinforced with nanoparticles of Al2O3, ZrO2, and graphite. Measurements were carried out before and after step by step isochronal thermal treatment at increasing temperature. A decrease in the grain size and secondary phases increase the strain independent component of the decrement. Microstructure changes due to thermal treatment are responsible for an increase of the strain dependent component of the decrement.