Enhanced Elevated-Temperature Strength in Refractory Complex Concentrated Alloys via Temperature-Induced Transition from Screw-to-Edge Dislocation Control

TL;DR

This study reveals a temperature-induced transition from screw- to edge-dislocation control in refractory alloys, leading to enhanced high-temperature strength and a new design approach for ultrahigh-temperature materials.

Contribution

It demonstrates a temperature-driven transition in dislocation control in RCCAs, resulting in improved strength at high temperatures, supported by experimental and simulation evidence.

Findings

Strength plateau at intermediate temperatures

Yield strengths surpass other RCCAs and superalloys above 1273 K

Crossover near ~900 K with edge dislocation dominance

Abstract

Refractory complex concentrated alloys (RCCAs) show promise for high-temperature applications but often lose strength due to screw-dislocation-controlled plasticity. We demonstrate a temperature-driven transition from screw- to edge-dislocation-controlled deformation in a single-phase NbTaTiV RCCA. Tensile tests from 298-1573 K reveal a pronounced intermediate-temperature strength plateau and yield strengths surpassing other ductile RCCAs and the Ni-based superalloy CMSX-4 above 1273 K. In-situ neutron diffraction, TEM, and molecular dynamics identify a crossover near ~900 K, where edge dislocation glide stabilized by V-induced lattice distortion dominates, enabling enhanced strength retention and a clear design strategy for ultrahigh-temperature applications.