Mechanical and damping behaviour of Al-20Zn based composites reinforced with recycled steel particles

Low materials-processing cost lightweight structural materials that combine good mechanical, damage tolerance and damping characteristics are of crucial demand for more sustainable design of reliable stress bearing components for the aerospace and automobile industries. The present investigation employs the use of typically high damping Al-20Zn alloy reinforced with recycled steel machining chips to ascertain the feasibility of achieving the aforementioned rare combination of material characteristics. The Al-20Zn composites were processed containing 6 and 8 wt% steel particles (derived from ball milling of steel machining chips), adopting stir casting practice. The properties evaluation spanned hardness, tensile properties, fracture toughness and damping assessment, and scanning electron microscopy (SEM) for microstructural characterization. Progressive increase in the hardness (45–75%), ultimate tensile strength (9–18%), and specific strength (0.2–5%) of the composites with increase in steel particles were recorded; with particle and interface strengthening linked to these improvements. Reductions in percentage elongation (28–37%) and fracture toughness (4–9%) were observed for the same steel reinforcement compositions, however the values were within the range for most metallic material reinforced AMCs reported in literature. The damping capacity of the Al-Zn based composites were comparable to the Al-20Zn alloy at temperatures up to 100 °C. The composites offered better balance of strength, toughness and damping properties in comparison with the unreinforced Al-Zn alloy, hence their practical applicability for stress bearing components design was considered promising.