Design metastability in high-entropy alloys by tailoring unstable fault energies

Abstract

Metastable alloys with transformation-/twinning-induced plasticity (TRIP/TWIP) can overcome the strength-ductility trade-off in structural materials. Originated from the development of traditional alloys, the intrinsic stacking fault energy (ISFE) has been applied to tailor TRIP/TWIP in high-entropy alloys (HEAs) but with limited quantitative success. Here, we demonstrate a strategy for designing metastable HEAs and validate its effectiveness by discovering seven alloys with experimentally observed metastability for TRIP/TWIP. We propose unstable fault energies as the more effective design metric and attribute the deformation mechanism of metastable face-centered cubic alloys to unstable martensite fault energy (UMFE)/unstable twin fault energy (UTFE) rather than ISFE. Among the studied HEAs and steels, the traditional ISFE criterion fails in more than half of the cases, while the UMFE/UTFE criterion accurately predicts the deformation mechanisms in all cases. The UMFE/UTFE criterion provides an effective paradigm for developing metastable alloys with TRIP/TWIP for an enhanced strength-ductility synergy.

Deformation mechanisms in high entropy alloys: a minireview of short-range order effects

“…In HEAs, metastability offers a pathway to tailor this transformation-or twinning-induced plasticity (TRIP/ TWIP). 70,71 During the deformation of TWIP/TRIP HEAs, martensite or twin formation provide alternative pathways for partial dislocation glide, while the phase or twin boundary reduces the dislocation mean free path, leading to the dynamic Hall-Petch effect. The competing deformation mechanisms in FCC HEAs enabled by metastability, such as dislocation glide, twinning, and martensitic transformation, can be predicted by the generalized stacking fault energy (GSFE) landscape and its variants (e.g., the generalized planar fault energy landscape, see Fig.…”

The Printability, Microstructure, and Mechanical Properties of Fe80−xMnxCo10Cr10 High-Entropy Alloys Fabricated by Laser Powder Bed Fusion Additive Manufacturing

“…Li et al further expanded this concept by adjusting the Mn content in metastable FeMnCoCr HEAs to modulate the stacking fault energy of the matrix phase, thereby increasing the driving force (ΔG) for austenite-to-martensite (γ→ε) transformation within the matrix [ 16 ]. By promoting a dual-phase microstructure through composition design in FeMnCoCr HEAs, various mechanisms such as transformation-induced plasticity (TRIP), solid-solution lattice distortion, and dislocations can be utilized to strengthen their mechanical properties and overcome trade-offs between strength and ductility [ 22 , 23 ].…”

Strength–ductility materials by engineering a coherent interface at incoherent precipitates

“…Simultaneously, possessing superior strength and excellent ductility has been in imperious demand, as it defines the ability of an alloy to resist fracture in advanced applications at extreme conditions. Breaking through the strength-ductility trade-off dilemma is a significant challenge in the materials science community [1][2][3] .…”