A novel in-situ polymer derived nano ceramic MMC by friction stir processing

• Polymer derived in-situ metal matrix composite was developed by friction stir processing.
• Nano PDC particles are distributed in the copper matrix.
• A fracture mechanism of PDC particles in multi pass FSP of composites has been proposed.
• Five times increase in micro hardness has been achieved from FSP in-situ PD-MMC.
• Using polymer route, zero wear of FSP tool has been reported for fabrication of MMC.

Friction stir processing (FSP) is a solid state technique used for material processing. Tool wear and the agglomeration of ceramic particles have been serious issues in FSP of metal matrix composites. In the present study, FSP has been employed to disperse the nanoscale particles of a polymer-derived silicon carbonitride (SiCN) ceramic phase into copper by an in-situ process. SiCN cross linked polymer particles were incorporated using multi-pass FSP into pure copper to form bulk particulate metal matrix composites. The polymer was then converted into ceramic through an in-situ pyrolysis process and dispersed by FSP. Multi-pass processing was carried out to remove porosity from the samples and also for the uniform dispersion of polymer derived ceramic particles. Microstructural observations were carried out using Field Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM) of the composite. The results indicate a uniform distribution of ~ 100 nm size particles of the ceramic phase in the copper matrix after FSP. The nanocomposite exhibits a five fold increase in microhardness (260HV100) which is attributed to the nano scale dispersion of ceramic particles. A mechanism has been proposed for the fracturing of PDC particles during multi-pass FSP.

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