Effect of oxygen content on the microstructure, compression properties and work-hardening behaviors of ZrCuAlNi glassy composites

Zr55Cu30Al10Ni5 bulk metallic glass (BMG) and its composites with different oxygen contents from 0.1 at% to 1.0 at% were prepared by copper-mold-casting. Primary crystallizing phases with different microstructures and volume fractions were produced in these alloys due to the incorporation of different oxygen contents. The X0.1 monolithic BMG has no plasticity. The X0.2, X0.3 and X0.4 composites contained the tiny crystallites or crystalline phases show some plasticity. The X0.2 composites exhibits the largest fracture strain of 8.10%. It is believed that the presence of the randomly distributed nanometer-sized crystallites in these alloys is effective to seed the formation and propagation of multiple shear bands. As the oxygen content increases from 0.5 to 1.0 at%, volume fraction of the crystalline phases in the composites increases remarkably, and the yield strength, fracture strength and fracture strain decreased, while Θ, Hc, K and n increased. The X0.5, X0.6, X0.8 and X1.0 composites display work-hardening and plastic deformation. The work-hardening effect and the plasticity result from the continuous martensitic transformation, the dislocation multiplication in the crystalline phase and the interactions of shear bands during deformation.