Influence of Pyrolysis Parameters on Microstructure and Mechanical Response of Polymer Derived and In Situ Ceramic Reinforced Aluminum Nanocomposite
摘要
This study explores use of polymer-derived ceramic as a solution to low toughness in aluminum nanocomposites. The reduced toughness in aluminum nanocomposites arises from particle agglomeration, the formation of brittle intermetallics, and weak particle–matrix interfaces. In this work, polymethyl hydrogen siloxane, a preceramic polymer, was dispersed into commercially pure aluminum using friction stir processing (FSP) and subsequently pyrolyzed to obtain a nanocomposite. The influence of pyrolysis temperature and duration (ranging from 300-600 °C and 1-10 h) on the microstructure and mechanical behavior was investigated. A differential scanning calorimeter was used to study the polymer-to-ceramic conversion. Pyrolysis resulted in a porous matrix due to gases released during polymer decomposition. A subsequent FSP pass was performed after pyrolysis to consolidate the matrix. Nanoscale dispersion of the particles was confirmed using electron microscopy, while grain size distribution was quantified using electron backscatter diffraction (EBSD) analysis. The tensile strength of the FSPed composite increased with increasing pyrolysis temperature and duration. Under optimal conditions (500 °C for 10 h), the tensile strength reached 240 MPa, representing a 240% increase compared to the base metal. The toughness of the composite also improved by 50%, reaching 54 MJ/m3. The Orowan mechanism was identified as the dominant strengthening mechanism due to the high fraction of nanoparticles.