Microstructural heterogeneities governing the deformation of Cu_47.5Zr_47.5Al₅ bulk metallic glass composites

Cu_47.5Zr_47.5Al₅ rods with different volume fractions of crystalline B2 CuZr phase were prepared by copper mould casting. Based on microstructural investigations a solidification mechanism is proposed for these bulk metallic glass (BMG) composites. The composite microstructure enhances the compressive plasticity (plastic strain up to 14%) and both plastic strain as well as yield strength scale with the crystalline volume fraction. Yield strength and fracture strain were successfully calculated using a strength model, which considers percolation and an empirical three microstructural element body approach, respectively. Furthermore, B2 CuZr was synthesized by means of a thermal cycling treatment and uniaxial compression tests were carried out at room temperature. The intrinsic work-hardenability caused by a martensitic transformation has strong implications on the deformation behaviour of the investigated Cu_47.5Zr_47.5Al₅ BMG composites.