Zr61Ti2Cu25Al12 bulk metallic glass under three-point bending: Characteristic of large-deflection deformation

Abstract

With three-point bending (3 PB) approach, nonlinear large-deflection deformation in bending was investigated for Zr61Ti2Cu25Al12 (ZT1) metallic glass (MG) beams with varying thickness from 1 mm to 100 μm. It was shown that higher flexibility is achievable by increasing the span-to-thickness ratio, which is desired for flexible members subjected to large-deflection performance. Moreover, yielding event of the MG beams in large-deflection situation can be captured via a conversion of load-deflection response into the non-dimensional form. Meanwhile, intrinsic sources responsible for the buckling events can be justified in terms of theoretical analytical solutions in mechanics. With monotonic bending and nonlinear bending theory, flexural yield strength of ZT1 MG with a thickness of 100 μm was determined to be 2050 MPa. Its bending proof strength at 0.005% permanent strain (σp,0.005%) was determined to be 1900 MPa, indicating that the beam-thickness effect on σp,0.005% is absent at least when the thickness was reduced from 1 mm down to 100 μm. As noticed, the response at σp,0.005% physically correlates with the propagation stress of embryonic shear bands, instead of the nucleation stress. In comparison with the current candidate materials in compliant mechanisms, ZT1 MG exhibits significant advantages in the components that the large-deflection elastic bending and high elastic-strain energy storage are desired.