Effect of annealing on the mechanical properties and fracture mechanisms of a Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 bulk-metallic-glass composite

The effect of annealing on the mechanical properties and fracture mechanisms of a Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 bulk-metallic-glass (BMG) composite subjected to tension and compression was investigated. When the BMG composite was annealed at high temperature, its mechanical properties changed greatly no matter whether tested under tension or compression. Under tensile loading, the as-cast specimen and the specimen annealed at 573 K failed in a shear mode with certain plasticity, but the specimens annealed at 593 K, 623 K, and 693 K for 1 h are very brittle and always failed in mode I fracture. Under compressive loading, however, all specimens failed in a shear mode with a fracture angle smaller than 45 degrees and the corresponding plasticity decreased with increasing the annealing temperature. Therefore, significant asymmetry phenomena between the failure mode, the fracture strength, and the plasticity are found in the BMG composite annealed at different temperatures. Based on the experimental results available, we propose that the ratio of the intrinsic shear strength to the cleavage strength is a substantial parameter controlling not only the strength asymmetry, but also the failure mode and the plastic deformation in the BMG composite.