Mg_2Si/Mg Composite Material via Solid-State Synthesis Processing

摘要

The solid-state synthesis of Mg_2Si from the premixed magnesium (Mg) and silicon (Si) powders or chips has been established by powder metallurgical (P/M) process. The effects of powder characteristics and cold compacting conditions on the behavior in synthesizing Mg_2Si wereclarified by Differential Scanning Calorimetory (DSC) thermal analysis and X-ray diffraction (XRD). Mg matrix composite alloys with Mg_2Si particles have been developed via the solid-state synthesis process. Mg_2Si particles are formed by pre-heating the Mg/Si green compact at 793K-853K before hot working such as forging or hot extrusion process, and are dispersed uniformly in the Mg matrix. The influence of Mg_2Si dispersions on microstructures, mechanical and wear properties of the composite material was investigated. The Mg composite shows high Young's modulus of 45-55GPa and hardness of 60-100HRE after hot forging due to the fine and hard Mg_2Si dispersions. In employing SiO_2 instead of Si particles, Mg_2Si/MgO/Mg alloy can be fabricated by using the deoxidizing process of SiO_2 by Mg and the Mg_2Si synthesis in solid-state. For example, the hot extruded Mg-4%SiO_2 alloy, which includes Mg_2Si and MgO dispersions, reveals UTS of 320MPa and elongation of over 4%. The uniform distribution of them in the Mg matrix also causes a superior tribological property with low and stable friction coefficient under wet wear test conditions in employing both S35C steel and AZ91 magnesium alloy as counter materials.