Effect of melt temperature on microstructural and strength properties of in-situ aluminum metal matrix composites containing SiCNO particles

Polymer Injection Pyrolysis (PIPs) can be adopted to synthesize in-situ ceramic particles within molten metal by stir-casting process. This paper investigated the effect of pyrolysis temperatures on microstructural and strength properties of in-situ aluminum matrix composites containing 2.5 vol% of SiCNO particles. In-situ composites were synthesized by stir-mixing of cross-linked polysilazane at four different pyrolysis temperatures (675–850°C) at which in-situ pyrolysis occurred and then followed by ultrasonic agitation and squeeze casting process. Microstructural data reveals that grain size and the particle size of SiCNO particles decreases with increasing the temperature of the melt at which polymer was introduced into the melt. The increase in the strength properties of the fabricated composites as compared to pure aluminum is almost 210% for the composites fabricated at 850°C while it is marginally 17% for the composites fabricated at 720°C. Fractography studies suggest that composite fabricated at 675°C exhibits a better combination of yield strength and ductility

Microstructure and compression behavior of chip consolidated magnesium

Chips produced by turning a commercial purity magnesium billet were cold compacted and then hot extruded at four different temperatures: 250, 300, 350, and 400 degrees C. Cast billets, of identical composition, were also extruded as reference material. Chip boundaries, visible even after 49: 1 extrusion at 400 degrees C, were observed to suppress grain coarsening. Although 250 degrees C extruded chip-consolidated product showed early onset of yielding and lower ductility, fully dense material (extruded at 400 degrees C) had nearly 40% reduction in grain size with 22% higher yield strength and comparable ductility as that of the reference. The study highlights the role of densification and grain refinement on the compression behavior of chip consolidated specimens