Microstructural and Mechanical Improvements in A356 Composites on Incorporating Polymer Derived Ceramics Through Ultrasonication at Semi-solid and Liquid State
摘要
This research investigates the fabrication of in-situ A356 matrix composites reinforced with polymer-derived ceramics via ultrasonication at semi-solid (620 °C) and liquid-state (720 °C) temperatures. A fixed volume percentage of 2.5% cross-linked polymer was injected into the molten A356 using ultrasonic-assisted stir casting. Microstructural analysis revealed a significant grain refinement in the composite fabricated at 620 °C, with grain sizes approximately 30% smaller compared to the 720 °C composite and the as-cast A356. XRD analysis of the composite synthesized at 620 °C did not manifest an Mg2Si peak, implying the likelihood of this phase formation only at temperatures surpassing 650 °C. The 620 °C composite also exhibited a 44% increase in hardness compared to the 720 °C composite. While the yield strength of the 720 °C composite showed a marginal improvement, the 620 °C composite demonstrated a substantial 20% increase in yield strength without a noticeable reduction in ductility, attributed to the uniform dispersion of SiOC particles. This study highlights the benefits of combining ultrasonication and semi-solid processing for enhancing the microstructure and mechanical properties of A356-SiOC composites.