Microstructural and mechanical properties of nanocrystalline (Al+12.5 at.%Cu)3Zr alloys synthesized by planetary ball milling and spark plasma sintering

The consolidation behavior and the mechanical properties of L12 phase (Al+12.5 at.%Cu)3Zr intermetallic powders with a nanocrystalline microstructure were investigated. The (Al+12.5 at.%Cu)3Zr powders prepared by Planetary Ball Milling (PBM) could be consolidated to full density by Spark Plasma Sintering (SPS) at 580 °C. This temperature is 300–400 °C lower than the conventional consolidation temperature of zirconium trialuminide. The L12 phase was maintained during the SPS process. The average grain size of the L12 phase specimens was 8.9 nm which is one of the smallest grain sizes ever reported for the nanocrystalline bulk specimens prepared by various consolidation methods. The micro-hardness was measured to be 975.8 Hv and this value was almost three times higher than that of the micro grain sized specimen. On the other hand, the average fracture toughness was lower than that of larger-grain bulk specimens. This result indicated that refining the grain size to a nano level was not beneficial for increasing the fracture toughness of brittle intermetallics. However, it was found that the fracture toughness could be enhanced by introducing heat-treatment after consolidation.