Contribution of Lattice Distortion to Solid Solution Strengthening in a Series of Refractory High Entropy Alloys

Abstract

We present an experimental approach for revealing the impact of lattice distortion on solid solution strengthening in a series of body-centered (bcc) Al-containing, refractory high entropy alloys from the Nb-Mo-Cr-Ti-Al system. By systematically varying the Nb and Cr content, a wide range of atomic size difference as a common measure for the lattice distortion was obtained. Single phase, bcc solid solutions were achieved by arc-melting and homogenization as well as verified by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The atomic radii of the alloying elements for determination of atomic size difference were recalculated on the basis of the mean atomic radii in and the chemical compositions of the solid solutions. Microhardness at room temperature correlates well with the deduced atomic size difference. Nevertheless, the mechanisms of microscopic slip lead to pronounced temperature dependence of mechanical strength. In order to account for this particular feature, we present a combined approach, using microhardness, nanoindentation and compression tests. The athermal proportion to the yield stress of the investigated equimolar alloys is revealed. These parameters support the universality of this aforementioned correlation. Hence, the pertinence of lattice distortion for solid solution strengthening in bcc high entropy alloys is proven.

High Throughput Discovery and Design of Strong Multicomponent Metallic Solid Solutions

“…Although the high-throughput idea is not new for HEAs 6 , 17 , CALPHAD simulations, for example, are a high-throughput method for predicting phase equilibria that are used in HEA alloy design 6 , 10 , 18 . Alloying 19 and microstructural 20 evolution have also been linked to strength, but we could not find an example of targeted alloy design for the prediction of HEA solid solution strengthening, the key strengthening mechanism in these alloys, in which a significantly stronger composition was designed based upon prediction . Studies exist that show stronger compositions are not necessarily the ones with the highest entropy, and these alloys are also not necessarily equiatomic 21 .…”

Enhanced Strength of a Mechanical Alloyed NbMoTaWVTi Refractory High Entropy Alloy

“…Han et al have successfully synthesized TiNbMoTaW and TiVNbMoTaW refractory HEAs. It is found that the addition of Ti with the largest atomic size significantly improves the mechanical properties of HEAs at room and elevated temperature [6,7]. …”

High-temperature materials for structural applications: New perspectives on high-entropy alloys, bulk metallic glasses, and nanomaterials

“…41 Figure 1. Yield strength (σ 0.2 ) of several refractory high-entropy alloys [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] (HEAs) and conventional stainless steel, aluminum, titanium, and nickel-based alloys. As potential high-temperature materials for structural applications, the HEAs show greater strength.…”