Strain Rate Dependence of Tensile Behavior in Hypoeutectic Zr-Cu-Al Bulk Metallic Glass

Bulk metallic glasses (BMGs) have many unique mechanical properties, e.g. extremely high strength and bending ductility. However, very limited data are reported on tensile ductility on BMGs. Recently there has been interest in strain rate dependence of fracture behavior in BMGs, such as fracture strength, plastic deformation and shear band formation. Meanwhile, we indicated that a hypoeutectic Zr-Cu-Al BMG shows longer and many shear bands and higher fracture toughness than a eutectic Zr-Cu-Al BMG. In this study, tensile test on a hypoeutectic Zr-Cu-Al BMG is performed under several different strain rates. Effect of strain rate on the mechanical properties such as tensile strength and Young's modulus are investigated. Also, it is ascertained whether the tensile plastic elongation in the hypoeutectic Zr-Cu-Al BMG occur or not. The hypoeutectic Zr-Cu-Al BMG is fabricated by an arc-tilt casting method. Chemical composition is Zr60Cu30Al10 at%. Tensile test is carried out under several strain rates. As a result, it was found that Young's modulus, tensile strength and elastic strain are about 90 GPa, 1700 MPa and 2%, respectively. Also the tensile specimen fractured with the shear plane inclined 52-55 degree for the loading axis. All these values were independent on the strain rate. Under any strain rate, the tensile plastic elongation did not occur and the multiple shear bands were not observed in the specimen surface.