Achieving high-strength magnesium matrix nanocomposite through synergistical effect of external hybrid (SiC plus TiC) nanoparticles and dynamic precipitated phase

摘要

Hybrid (SiC+TiC) p/AZ91 nanocomposites were successfully fabricated by the combination of semisolid stirring and ultrasonic vibration. Then the nanocomposites were extruded at a low temperature of 270 degrees C with slow extrusion speeds of 1, 0.5 and 0.1 mm/s, respectively. The result showed that the distribution of hybrid nanoparticles was uniform both in the as-cast and as-extruded conditions. With decreasing the extrusion speed from 1 mm/s to 0.1 mm/s, the grain sizes of the nanocomposites were gradually decreased. The volume fraction of precipitated Mg17Al12 phases was gradually increased while the average diameter was decreased. The externally applied hybrid nanoparticles and dynamic precipitated Mg17Al12 phase could hinder the movement of grain boundary, contributing to the grain refinement. The yield strength of similar to 345.6 MPa, ultimate tensile strength of similar to 397.2 MPa and elongation of similar to 5.2% was obtained in case of the nanocomposite extruded at 0.1 mm/s. The increment in the strength could be attributed to the addition of hybrid (SiC+TiC) nanoparticles, ultra-fine matrix grains and large amount of precipitated Mg17Al12 phases. For the stage. on the work hardening rate curve for the (SiC+TiC) p/AZ91 nanocomposite, the hybrid nanoparticles and dynamic precipitated Mg17Al12 could impede the annihilation of dislocation while the refined matrix grains had the opposite effects. (C) 2018 Elsevier B.V. All rights reserved.