A precipitation-hardened high-entropy alloy with outstanding tensile properties

Abstract

a b s t r a c tRecent studies indicated that high-entropy alloys (HEAs) possess unusual structural and thermal features, which could greatly affect dislocation motion and contribute to the mechanical performance, however, a HEA matrix alone is insufficiently strong for engineering applications and other strengthening mechanisms are urgently needed to be incorporated. In this work, we demonstrate the possibility to precipitate nanosized coherent reinforcing phase, i.e., L1 2 -Ni 3 (Ti,Al), in a fcc-FeCoNiCr HEA matrix using minor additions of Ti and Al. Through thermomechanical processing and microstructure controlling, extraordinary balanced tensile properties at room temperature were achieved, which is due to a well combination of various hardening mechanisms, particularly precipitation hardening. The applicability and validity of the conventional strengthening theories are also discussed. The current work is a successful demonstration of using integrated strengthening approaches to manipulate the properties of fcc-HEA systems, and the resulting findings are important not only for understanding the strengthening mechanisms of metallic materials in general, but also for the future development of high-performance HEAs for industrial applications.

On the strain rate-dependent deformation mechanism of CoCrFeMnNi high-entropy alloy at liquid nitrogen temperature

“…Hong et al [11] suggested that the strong temperature dependence of yield stress and the small V* in CoCrFeMnNi favor dislocation glide over the obstacles with high friction stress. Interestingly, the V* of the CoCrFeMnNi alloy in this study is close to those observed in BCC metals (8-100b 3 ) and HCP metals (5-100b 3 ) [11]. It was reported [11] that the increase in V* with strain supports the deformation mechanism overcoming nanoscale inhomogeneities, such as co-clusters and/or short-range orderings (SROs), as the rate-controlling mechanism.…”

“…Lu et al [29,30] reported that, when twin spacing decreases from the micrometer to the nanometer range, the V* for nanotwinned Cu decreases significantly from 1000b 3 to 10b 3 . Lu et al [29,30] observed the appreciable formation of steps and jogs along twin boundaries, and the generation of high dislocation density around twin boundaries, especially in the vicinity of stress concentrations.…”

“…The four core effects of the HEAs, that is, high configuration entropy, sluggish diffusion, cocktail effect, and large lattice distortion [2], lead to their promising properties, such as high strength and ductility, good corrosion resistance, and superior fracture toughness [3][4][5].…”

Phase separation of metastable CoCrFeNi high entropy alloy at intermediate temperatures

“…In the past decade, many researchers took the CoCrFeNi HEA as a base alloy and designed lots of new alloys by adding alloying elements [6,7,[19][20][21][22][23][24][25]. He et al [19] found that the CoCrFeNi HEA alloy can be strengthened from 400 MPa to 1300 MPa by adding Ti and Al elements. By adding Al element into the CoCrFeNi base, Ma et al obtained fcc single crystals of CoCrFeNiAl0.3 HEA with an ultimate tensile elongation of 80% [26].…”

Nanostructured multielement (TiHfZrNbVTa)N coatings before and after implantation of N+ ions (1018cm−2): Their structure and mechanical properties

“…Nitride coatings from HEA have received particular attention because of improved physical and mechanical characteristics. Most of HEA nitrides consist of 5, 6 or 7 elements, but they can incorporate up to 19 elements [38][39][40][41][42][43][44][45] resistance remains still largely unexplored. For the last few years several papers, devoted to the influence of Cu -, Au -, N + ion implantation on hardness, plasticity index and corrosion resistance were published [46][47][48][49][50].…”