Ultra-High Dynamic Strength of Additively Manufactured GRX-810 Under Coupled Conditions of High Strain Rate and Elevated Temperature

TL;DR

This study reveals that the CrCoNi-based ODS-MPEA alloy GRX-810 exhibits ultra-high strength at high strain rates and ambient temperature, but softens at elevated temperatures due to dislocation confinement and thermal effects.

Contribution

It provides the first detailed analysis of the high strain rate and elevated temperature deformation mechanisms of GRX-810 ODS-MPEA alloy, highlighting the role of oxide dispersion.

Findings

GRX-810 ODS shows 2.79 times higher strength at high strain rates and ambient temperature.

Thermal softening occurs at high strain rates and elevated temperatures due to dislocation confinement.

Oxide dispersion contributes to athermal strengthening, which diminishes with temperature.

Abstract

Deformation mechanisms in CrCoNi-based oxide-dispersion-strengthened multi-principal element alloys (CrCoNi-based ODS-MPEA) have been extensively studied under quasi-static and low strain rate loading over a wide temperature range, yet their behavior at high strain rates and elevated temperatures remains poorly understood. In this work, we investigate the high strain rate response of the CrCoNi-based ODS-MPEA alloy GRX-810 and its non-ODS variant. The ODS variant contains a high density of hexagonal yttria nanoparticles that serve as the strengthening oxide phase. At high strain rates and ambient temperature, GRX-810 ODS exhibits higher dynamic strength, approximately 2.79 times its quasi-static strength, than both conventional alloys and its non-ODS variant because of the additional athermal strengthening provided by the nanoscale oxide dispersion. At high strain rates and elevated temperatures, however, GRX-810 ODS undergoes thermal softening. This response is consistent with dislocation confinement associated with the small interparticle spacing of the oxide dispersion, which limits the phonon-drag contribution, together with the temperature-dependent reduction of elastic constants that lowers the athermal strengthening terms, including the oxide-related contribution. Additional weakening of the solute-pinning mechanism at elevated temperature further reduces the dynamic yield strength.