Thermal and mechanical properties of mechanically alloyed 304LSS-CNT metal matrix composites

A methodology for the creation of 304LSS-CNT metal matrix composites using the mechanical alloying approach is presented. Planetary ball milled powders were both melted and hot pressed and achieved up to 96% theoretical density. High resolution scanning electron microscopy, Scanning Transmission Electron Microscopy, X-ray diffraction, energy dispersive spectroscopy, thermal diffusivity measurements, and Vickers microhardness measurements are used to characterize as processed and heat treated composites. Melted and solidified samples show highly anisotropic austenite/martensite microstructures with the presence of large dendritic carbon agglomerations, while hot-pressed samples show equiaxed austenite/martensite grains with a large number density of carbide precipitates. Grain size and thermal diffusivity decrease while microhardness increases up to 36% with up to 2% carbon nanotube addition for hot-pressed samples. Thus, mechanical alloying has been shown to be a potential option for the production of homogeneous 304LSS-CNT metal matrix composites for applications requiring increased strength.