Pressure Assisted Development and Characterization of Al-Fe Interface for bi-metallic Composite Castings: An Experimental and Statistical Investigation for Low Pressure Regime

Review of the available literature indicates that development of metal reinforced castings present intriguing prospects but carry inherent challenges owing to differences in thermal coefficients, chemical affinities, diffusion issues and varying nature of intermetallic compounds. It is supported that pressure application during solidification may favorably influence the dynamics of the aforementioned issues, nevertheless, not only certain limitations have been cited but also some pressure and process regimes have not been found to be investigated and optimized. This work employs the pressure-assisted approach for bi-metallic steel reinforced aluminum composite castings at low-pressure regime and thoroughly investigates the role of three process parameters namely pouring temperature (800°C-900°C), pressure (10–20 bars) and holding time (10–20 sec) for producing sound interfaces. Taguchi L9 orthogonal array has been employed as DOE while dominant factors have been determined via ANOVA and Grey relational analysis multi-objective optimization technique. Supplementary analysis through optical micrographs, SEM and EDS has been relied upon to quantify interfacial layer thicknesses and to study microstructural and compositional aspects of the interface. Nano-indentation tests under static and dynamic loading have also been performed for mechanical strength characterization. It has been found that uniform interfaces with verifiable diffusion are obtainable with pouring temperature being the most influential parameter (PCR 92.84%) in this pressure regime. Optimum parameters determined from the work, yield ~ 328% thicker interface layer, 19.42% better nano-hardness and 19.10% improved cooling rate when compared to the process conditions with least parametric levels.