Comparison of theoretical and experimental physio-mechanical properties of coal-fly ash (CFA) reinforced iron matrix composites

In this work, the effect of coal-fly ash (CFA) reinforcements on the physio-mechanical properties of iron metal matrix composites (IMMCs) are predicted and compared with the experimental results. The IMMCs were synthesized by reinforcing different amounts (0, 0.15, 0.28 and 0.38 vol. %) of CFA particulates to the iron matrix through powder metallurgy technique (P/M). The iron powder/CFA mixtures were compacted at a load of 10 ton followed by sintering in inert environment at 1150 ℃ for 90 min. Structural, morphological, and elemental characterisation of iron/CFA and IMMCs were performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and Energy Dispersive X-Ray spectroscopy (EDS) respectively. Sufficient diffusion among the iron particles, uniform distribution of CFA particulates and clear interfaces between matrix and reinforcements have been observed in the FESEM micrographs. The trends of experimental results of sintered density and microhardness of the IMMCs has been found in line with the theoretical results predicted using rule of mixtures (ROM). Furthermore, the effects of increased vol.% of CFA inclusions on the elastic modulus \((E)\), yield strength \(({\sigma }_{y}\)) and ultimate tensile strength \({(\sigma }_{u})\) of the IMMCs have been conceived using Ramberg–Osgood (RO) model, under tensile loading. A significant reduction of 32% in sintered density and 42% increment in microhardness of the IMMCs have been observed. The RO model demonstrated significant enhancements of 51% in \(E\) and 42% in \({\sigma }_{y}\). On the other hand, whereas 44% reduction in ultimate tensile strength of IMMCs has been observed on increased amount of CFA (0–0.38 vol.%). The load transfer strengthening mechanism has been found dominating the Hall–Petch followed by Taylor’s strengthening mechanism. Further, the various specific properties of the IMMCs were compared with prevalent literature. The specific properties of IMMCs such as microhardness, \(E\), \({\sigma }_{y}\) and \({\sigma }_{u}\) are found comparable with the established aluminium based MMCs.