A strong and ductile medium-entropy alloy resists hydrogen embrittlement and corrosion

Abstract

Strong and ductile materials that have high resistance to corrosion and hydrogen embrittlement are rare and yet essential for realizing safety-critical energy infrastructures, hydrogen-based industries, and transportation solutions. Here we report how we reconcile these constraints in the form of a strong and ductile CoNiV medium-entropy alloy with face-centered cubic structure. It shows high resistance to hydrogen embrittlement at ambient temperature at a strain rate of 10−4 s−1, due to its low hydrogen diffusivity and the deformation twinning that impedes crack propagation. Moreover, a dense oxide film formed on the alloy’s surface reduces the hydrogen uptake rate, and provides high corrosion resistance in dilute sulfuric acid with a corrosion current density below 7 μA cm−2. The combination of load carrying capacity and resistance to harsh environmental conditions may qualify this multi-component alloy as a potential candidate material for sustainable and safe infrastructures and devices.

Effects of cryogenic temperature on tensile and impact properties in a medium-entropy VCoNi alloy

“…The V element has a larger misfit volume than other alloy elements, which consequently results in further lattice distortion and strength, as demonstrated via ab initio calculations and solute strengthening theories [6] . Furthermore, the VCoNi alloy is known to possess functional properties, such as superplasticity [7] , as well as high resistance to corrosion and hydrogen embrittlement [8] . These remarkable mechanical and functional properties facilitate the application of these alloys to sustainable infrastructures and devices.…”

A mechanically strong and ductile soft magnet with ultralow coercivity

“…2c). The relatively large grain size (~85 µm) of the current M-MCA enables higher mobility of dislocations compared to most of the previously reported strong MCAs that had smaller grain size [22][23][24] (~10 µm). Further straining (𝜀 +,-=30%) refines the crystallographically aligned microbands (Extended Data Fig.…”

“…More importantly, the coercivity of the new material is lower than that of all NiFe alloys and other MCAs, comparable only to Fe-Si, CoFe 29,30 , CoFe 31,32 , SiFe 33 , Fe 34 , amorphous alloys 4,[35][36][37] and established MCAs [38][39][40][41][42][43][44][45][46][47][48][49] . b, Ashby map showing σ $%& ×ε ( versus average grain size compared to those of other strong and ductile MCAs [22][23][24][50][51][52][53] . 'am' in the legend stands for amorphous alloys.…”

Ultra-strong and strain-hardenable ultrafine-grained medium-entropy alloy via enhanced grain-boundary strengthening

“…The novel mechanical properties of the VCoNi alloy were derived from the concept of the enhanced solid-solution strengthening induced by the large difference in atomic radius in the V-Co-Ni system as compared with those in conventional alloys. Moreover, beyond the substantial merits for good mechanical properties, the VCoNi MEA exhibits multi-functional performances, such as high resistance to hydrogen embrittlement due to low hydrogen diffusivity [16], good corrosion resistance due to the absence of a local potential gradient [16], and high strain-rate superplasticity, achieved via active dynamic recrystallization at high temperatures [17].…”