Ultrafine-structured Ni-based bulk alloys with high strength and enhanced ductility

High-strength ultrafine eutectic-dendrite composites were produced from arc-melted ingots of a novel Ni-Hf alloy system. The composites are composed of micron-scale dendritic phases (Ni5Hf intermetallic phase or Ni solid solution) and an ultrafine lamellar eutectic matrix (Ni5Hf + fcc-Ni). The optimization of the Ni-Hf alloy composition is performed from the viewpoint of both high strength and ductility. The strongest Ni90Hf10 has an ultrafine lamellar eutectic structure and exhibits a high strength of 3.56 GPa and a plastic deformation of 34% under compression. In particular, the material's plasticity can be monotonically improved by reinforcing the ductile dendritic phases in the eutectic matrix. The high strength and ductility values can be achieved without using the injection mould casting or rapid solidification procedure. The microstructure-property relationship of these ultrafine-structured composites is also discussed here.