Fabrication of magnesium matrix composites using a spontaneous infiltration technique.

摘要

A new process was developed to fabricate particulate metal matrix composites (MMCs). The process involves two steps: (1) forming a particulate porous compact, and (2) introducing molten magnesium or magnesium alloy (AZ91) into the channel network by a spontaneous infiltration technique.; A uniform distribution of SiC particulates in magnesium matrix was achieved. Microsegregation existed in composites when the particle size of reinforcement was 38 mum and 22 mum, however, when the particle size of reinforcement was 12 mum, the microsegregation was eliminated.; The interfacial reaction between SiC and Mg studied by Scanning Electron Microscopy (SEM), microanalysis, and X-Ray Diffraction (XRD) techniques showed that, Mg reacted with Si or SiO2 to form Mg2Si, Mg 2Si was present at the surface of SiC after precipitation, resulting in improved wettability between Mg and SiC. As a result of this interfacial reaction, the infiltration process became spontaneous. The infiltration process was related to the infiltration temperature, SiC particle size and matrix chemistry. Increasing the infiltration temperature, decreasing the particle size of SiC resulted in more successful infiltration.; Mechanical testing conducted on composites revealed that the hardness and Ultimate Tensile Strength (UTS) of composites increased with the decrease of particle size of SiC and corresponded to an increase of the volume fraction of SiC.