Using diluted master nanocomposites to achieve grain refinement and mechanical property enhancement in as-cast Al–9Mg

The grain refinement and mechanical property enhancement in ultrasonically prepared metal matrix nanocomposites (MMNCs) were studied in an Al–9Mg matrix with TiC0.7N0.3 nanoparticle additions. Also, the ability to add pieces of previously prepared, higher concentration master MMNCs to melt for a lower final nanoparticle concentration MMNC was shown to be possible. Al–9Mg + 1.5 vol.% TiC0.7N0.3 nanocomposites were shown to have significantly reduced grain sizes and enhanced mechanical properties compared to the reference Al–9Mg samples. When pieces of the original Al–9Mg + 1.5 vol.% TiC0.7N0.3 were added to additional Al–9Mg melt for final nanoparticle concentrations of 0.2% and 0.5% by volume, much of the grain refinement and mechanical property enhancement was again observed. For comparison, samples were also made with a commercial Al–5Ti–1B grain refiner. The conventional Al–5Ti–1B grain refiner did achieve similar grain refinement; however this did not result in the same enhancement in strength and ductility. This “master nanocomposite” approach has great potential for bringing MMNC usage to the industrial stage.