Residual Stresses in Bulk Metallic Glasses due to Thermal Tempering

Abstract

Bulk metallic glasses (BMGs) are attractive structural materials that develop residual stresses during processing due to thermal tempering. In this process, compressive surface stresses are generated within thin layers balanced with tension in the interior. In the present study, stress generation was analyzed experimentally and theoretically in a BMG plate and a cylinder. The residual stresses were measured using the crack compliance method. It was shown that high stresses can be attained in metallic glasses due to thermal tempering: over −300 MPa compression on the surface balanced by +150 MPa tension in the middle. The experimental data were then compared to the predictions of a viscoelastic model that took into account the equilibrium viscosity of BMG as a function of temperature. The model was shown to be accurate within 5 to 25% of the experimental stress data. It is therefore a powerful tool for estimating processing-induced residual stresses in bulk metallic glasses.