Enhancing fatigue life by ductile-transformable multicomponent B2 precipitates in a high-entropy alloy

Abstract

Catastrophic accidents caused by fatigue failures often occur in engineering structures. Thus, a fundamental understanding of cyclic-deformation and fatigue-failure mechanisms is critical for the development of fatigue-resistant structural materials. Here we report a high-entropy alloy with enhanced fatigue life by ductile-transformable multicomponent B2 precipitates. Its cyclic-deformation mechanisms are revealed by real-time in-situ neutron diffraction, transmission-electron microscopy, crystal-plasticity modeling, and Monte-Carlo simulations. Multiple cyclic-deformation mechanisms, including dislocation slips, precipitation strengthening, deformation twinning, and reversible martensitic phase transformation, are observed in the studied high-entropy alloy. Its improved fatigue performance at low strain amplitudes, i.e., the high fatigue-crack-initiation resistance, is attributed to the high elasticity, plastic deformability, and martensitic transformation of the B2-strengthening phase. This study shows that fatigue-resistant alloys can be developed by incorporating strengthening ductile-transformable multicomponent intermetallic phases.

Phase-selective recrystallization makes eutectic high-entropy alloys ultra-ductile

“…3g . The ductile-transformable B2 phase 43 has been proven to enhance the fatigue life significantly in the duplex HEA 44 . In the present PSR EHEA, the phase transformation enhances the deformability of the B2 phase and promotes the coordinated deformation between the soft and hard phases, even with low content of transformation.…”

Multicomponent Precipitation and Strengthening in Intermetallic-Strengthened Alloys

“…The sublattice occupancy in the multicomponent precipitates was investigated by atomistic modelling, and the results indicate that these L1 2 -type multicomponent precipitates can be regarded as the (Ni 43.3 Co 23.7 Fe 8 ) 3 (Ti 14.4 Al 8.6 Fe 2 ) phase (Yang et al, 2018). In addition, multicomponent B2-(Ni,Co)(Al,Cr,Fe) precipitates strengthened high-entropy alloys are developed, which exhibit outstanding fatigue resistance (Feng et al, 2021). This research area is still immature and may lead to new exciting developments.…”

Fatigue Behavior and Mechanisms of High-Entropy Alloys

“…Similarly, efforts using hierarchical microstructures to improve LCF resistance of HEAs have been made as well. Recently, Feng et al [19] enhanced LCF life at low strain amplitudes in an Al 0.5 CoCrFeNi by incorporating hierarchically distributed multicomponent B2 precipitates into the FCC matrix. Due to the ductile-transformable nature of the multicomponent B2 precipitates, the fatigue-crack-initiation resistance can be greatly improved.…”

“…Recently, a new class of alloys termed as high-entropy alloys (HEAs) or medium-entropy alloys (MEAs) containing multi-principal elements have been developed, which divert away from the conventional alloys that are based on one or rarely two principal elements [3][4][5][6][7][8]. Due to their vast compositional space, HEAs offer new opportunities to chase desirable performances, demonstrated by the continuously found exceptional properties, such as high strength [9][10][11][12], outstanding cryogenic and ambient ductility [13][14][15], excellent fracture toughness [16], good fatigue resistance [17][18][19], great corrosion resistance [20,21], etc. Thus, HEAs have shown great potential practical applications as future structural materials, which in many cases will invariably depend on their fatigue resistance that determines component lifetimes.…”

“…Thus, HEAs have shown great potential practical applications as future structural materials, which in many cases will invariably depend on their fatigue resistance that determines component lifetimes. In pursuit of HEAs with exceptional fatigue resistance, efforts in studying the fatigue behavior of HEAs have been made recently [17][18][19][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Despite these works, a full clear picture of fatigue mechanisms in HEAs remains absent, mainly because of the varied fatigue testing conditions and various HEA systems in those reports.…”