Failure of Zr₆₁Ti₂Cu₂₅Al₁₂ bulk metallic glass under torsional loading

The torsional properties of the Zr₆₁Ti₂Cu₂₅Al₁₂ BMG have been tested using cylinder samples, including the shear yield strength, shear elastic strain limit and shear modulus. Under torsional loading, the BMG fails via a major shear band, without obvious macroscopic plasticity on the specimen surface. The shear band maintained stable propagation by a distance of ∼300 μm (∼20% of cylinder radius) before final catastrophic failure, owing to the constraint of stress gradient along the radial direction. The combined tensile, compressive and torsional properties of the Zr₆₁Ti₂Cu₂₅Al₁₂ BMG suggest that recent ellipse criterion and eccentric ellipse criterion are more appropriate than other well-known ones in describing the yield behavior of this BMG. The cooperative shear model underestimates the shear elastic strain limit, because of its default assumption that the yielding behavior follows the Tresca yield criterion.