Analysis of dynamic segregation and crystallisation in Mg65Cu25Y10 bulk metallic glass using atom probe tomography

Abstract

In order to develop an in-depth understanding of the flow behaviour and dynamic devitrification processes of metallic glasses in the supercooled liquid region, tensile testing of amorphous Mg65Cu25Y10 samples was carried out at temperatures from 150 to 170°C and at strain rates from 1×10−3s-1 to 1×10−2s−1. Tensile data showed a consistent and reproducible inflexion in flow stress at a particular strain that was largely independent of strain rate. This was followed by a dramatic increase in flow stress occuring prior to the determined onset times of static crystallisation. Samples were analysed using atom probe tomography and the results indicate that tensile straining of the initially homogeneous amorphous alloy results in segregation into two distinct glassy phases via a shear-related process, coincident with the maximum shear plane angle, followed by the evolution of regions corresponding to the composition of a number of equilibrium binary and ternary intermetallic phases.