Mapping the Strain Distributions in Deformed Bulk Metallic Glasses Using Hard X-Ray Diffraction

The deformation behavior of Cu-45 Zr-46.5 Al7Ti1.5 bulk metallic glass (BMG) under bending was investigated in-situ using high-energy X-ray synchrotron diffraction. Samples were bent using two different benders with radii of 10 and 20 mm. The components of the strain tensor were determined from the change of positions of the first maximum of the diffracted intensity in reciprocal space. The procedure of data treatment was improved by the introduction of direct beam off-center correction. Comparing results for the two different bending radii, we found that the zero stress region does not necessarily lay within the central part of the specimen. Bending with smaller radius resulted in symmetric strain distribution, whereas a larger bending radius revealed strong asymmetry. Furthermore, bending with a smaller radius (10 mm) shows steeper strain gradients as compared with the situation in which the larger bending radius (20 mm) was used. Using a smaller bending radius implies reaching higher tensile/compressive stresses and reveals the signs of the plastic deformation, which are demonstrated as a saturation of elastic strains.