Atomic and electronic basis for the serrations of refractory high-entropy alloys

Abstract

Refractory high-entropy alloys present attractive mechanical properties, i.e., high yield strength and fracture toughness, making them potential candidates for structural applications. Understandings of atomic and electronic interactions are important to reveal the origins for the formation of high-entropy alloys and their structure−dominated mechanical properties, thus enabling the development of a predictive approach for rapidly designing advanced materials. Here, we report the atomic and electronic basis for the valence−electron-concentration-categorized principles and the observed serration behavior in high-entropy alloys and highentropy metallic glass, including MoNbTaW, MoNbVW, MoTaVW, HfNbTiZr, and Vitreloy-1 MG (Zr 41 Ti 14 Cu 12.5 Ni 10 Be 22.5 ). We find that the yield strengths of high-entropy alloys and high-entropy metallic glass are a power-law function of the electron-work function, which is dominated by local atomic arrangements. Further, a reliance on the bonding-charge density provides a groundbreaking insight into the nature of loosely bonded spots in materials. The presence of strongly bonded clusters and weakly bonded glue atoms imply a serrated deformation of high-entropy alloys, resulting in intermittent avalanches of defects movement.

A brief review of data-driven ICME for intelligently discovering advanced structural metal materials: Insight into atomic and electronic building blocks

“…On the one hand, the hidden topological orders or short-range orders (SRO) or clusters or microstates should be considered when constructing the structures of multicomponent alloys theoretically and experimentally. The microstates/configurations/local orders are essential to reveal their structure-property relationship [49,50,51,52]. Predictive models have been proposed to reveal the hydrogen trapping and bubbling in nanovoids in bodycentered-cubic (BCC) metals, which integrate the multiscale calculations including DFT calculations, classical MD simulations, and kinetic Monte Carlo simulations [53].…”

“…Predictive models have been proposed to reveal the hydrogen trapping and bubbling in nanovoids in bodycentered-cubic (BCC) metals, which integrate the multiscale calculations including DFT calculations, classical MD simulations, and kinetic Monte Carlo simulations [53]. The microstates/clusters dominated shear bands or serrations of high-entropy alloys and metallic glasses during deformation are reported [51,54]. On the other hand, "defects at the atomic scale, which are revealed in the electronic structure, affect the macroscopic mechanical properties Figure 2: The proposed data-driven ICME approach [2,24] together with the corresponding foundations and milestones [24,36,39,40].…”

“…Moreover, with the guidance of the electron redistributions in terms of bonding charge density [56,65,66,67] and electron localization functions [68,69], new insights are provided into those microstates/SROs/clusters and structural phase transformations quantitatively and qualitatively. They are utilized to reveal the physical nature of chemical bond of pure metals (Al [61,70], Ag [71], Fe [60,72], Mg, Ti [73,74]), alloys (Co-based [57,62] and Ni-based [75]alloys), Fe-X alloys [60,72], Mg-RE-TM alloys [67,76], RHEAs [49,51], Ti-X alloys [73,74] [78], and Fe 3 O), semiconductors (graphene [65], sulfur [79], sulfides [79], and SiC [80]), and structural defects (stacking faults [62,73,81], APBs [57,75], grain boundaries [61,72], and dislocations [82,83]), which also reveal the fundamental solid-solution strengthening/embrittlement mechanism [61,73] and the grain refinement mechanism [70,74].…”

“…Referring to the VEC, the advantage of EWF is that these elements in the same group of elemental periodic table can be distinguished. Thus, EWF will be more suitable than VEC to be considered as one kind of key Figure 3: The periodic table of pure elements [51] with the corresponding EWF [63] and VEC [64].…”

“…Lattice distortion/misfit has been set as one of the four hypotheses in the discovery of advanced high-entropy alloys, which can be caused by the atomic radius differences among various solute/solvent and the local chemical orders/disorders [49,51]. It is understood that local chemical orders play an important role in the mechanical properties of HEA, such as serrations, strengthening, and functional applications [33,49,51,118,119,120]. Recently, improved experimental and theoretical tools to study short-range ordering effects have been highlighted [33].…”