Effect of relaxation and primary nanocrystallization on the mechanical properties of Cu60Zr22Ti18 bulk metallic glass

The dependence of the microscopic and macroscopic mechanical response of a Cu-based bulk metallic glass (BMG) on the degree of thermal relaxation and different crystalline volume fractions has been studied. The samples were characterised by constant-rate heating differential scanning calorimetry (DSC), macroscopic compression and nanoindentation tests. Macroscopic compression tests revealed that the fracture strength and Young's modulus increase with increasing annealing time, and therefore, with increasing crystalline volume fraction. However, embrittlement of the material is also found for longer annealing treatments. A perfect solute mixture model of defect-free nanoparticles embedded in an amorphous matrix was used to account for the strengthening effect. Nanomechanical tests have contributed to the understanding of the mechanical behaviour of the heat-treated BMG states under investigation.