Abstract:
In-situ Mg matrix composites are fabricated by combining both liquid- and solid-state processing routes. Firstly,
liquid polymer was injected into the molten Mg at a temperature of 800 °C to initiate pyrolysis. In-situ pyrolysis
aids in the conversion of liquid polymer into sub-micron sized SiCNO particles (mean particle size in the range
of 0.5–1 µm) and Mg2Si particles. Most of the polymer derived SiCNO particles were pushed by the
solidification front and as a result segregated at the grain boundaries of as-cast composites (mean grain size
in range of 50–65 µm) during subsequent solidification process. Formation of Mg2Si phase could be minimized
by reducing the pyrolysis temperature from 800 to 700 °C. Single pass friction stir processing (FSP) of these ascast composites lead to improved homogeneity in the SiCNO particle distribution, particle refinement (mean
particle size of about 200–300 nm) and grain refinement (mean grain size in range of 2.5–3.5 µm). Mechanical
properties (hardness, compressive yield stress, ultimate compressive stress, strain to failure and strain
hardening exponent) of the FS processed composites were enhanced significantly as compared to their ascast counterparts. Strengthening mechanisms and numerical models are being evoked to explain the observed
yield strength in these two stage processed composites.
