High-Temperature Nano-Indentation Creep Behavior of Multi-Principal Element Alloys under Static and Dynamic Loads

Abstract

Creep is a serious concern reducing the efficiency and service life of components in various structural applications. Multi-principal element alloys are attractive as a new generation of structural materials due to their desirable elevated temperature mechanical properties. Here, time-dependent plastic deformation behavior of two multi-principal element alloys, CoCrNi and CoCrFeMnNi, was investigated using nano-indentation technique over the temperature range of 298 K to 573 K under static and dynamic loads with applied load up to 1000 mN. The stress exponent was determined to be in the range of 15 to 135 indicating dislocation creep as the dominant mechanism. The activation volume was ~25b3 for both CoCrNi and CoCrFeMnNi alloys, which is in the range indicating dislocation glide. The stress exponent increased with increasing indentation depth due to higher density and entanglement of dislocations, and decreased with increasing temperature owing to thermally activated dislocations. The results for the two multi-principal element alloys were compared with pure Ni. CoCrNi showed the smallest creep displacement and the highest activation energy among the three systems studied indicating its superior creep resistance.

Ballistic Impact Response of Al0.1CoCrFeNi High‐Entropy Alloy

“…TEM was done on FEI Tecnai F20 operating at 200 kV. Nano‐indentation was performed on TI‐Premier (Bruker, USA) with a diamond Berkovich probe, at a load of 10 mN, loading and unloading rate of 2 mN s −1 , and hold time of 2 s. The spacing between the nano‐indents was kept at 50 μm to avoid overlapping of plastic zones of adjacent indents and for capturing nano‐indentation hardness maps over a large area with high resolution …”

Review of Powder Bed Fusion Additive Manufacturing for Metals

“…The large compositional design space of HEAs offers a unique flexibility to tailor their mechanical and functional properties for different applications. The core effects of high configurational entropy, lattice distortion, cocktail effect, and sluggish diffusion lead to a gamut of attractive mechanical, corrosion, and oxidation properties [328][329][330][331][332][333][334][335][336][337][338][339]. Therefore, they have been attracted as potential materials for advanced applications including aerospace, nuclear, cryogenics, and medical [340][341][342].…”

Complex Concentrated Alloys (CCAs)—Current Understanding and Future Opportunities

“…Eight research articles, four reviews, and one perspective have been published in this special issue of Metals. The subjects are multidisciplinary and divided into several topics including: (i) simulation and modeling for predicting structure and properties [1], (ii) unique deformation mechanisms in multi-principal alloys [2][3][4], (iii) microstructure and properties resulting from various processing routes [5][6][7][8][9][10], (iv) corrosion and surface degradation behavior [11,12], and (v) perspectives on ways to design mechanically and functionally advanced concentrated alloys [13]. Beyramali Kivy et al [1] reviewed the computational tools for studying the structure and properties of multi-principal alloys and identified the advantages as well as limitations of simulations in accelerating design and development of new alloys.…”

“…Beyramali Kivy et al [1] reviewed the computational tools for studying the structure and properties of multi-principal alloys and identified the advantages as well as limitations of simulations in accelerating design and development of new alloys. The unique deformation mechanisms of concentrated alloys are discussed in one review article and two research papers in this special issue [2][3][4]. Brechtl et al [2] reviewed the serration behavior during deformation in HEAs and its dependence on composition, microstructure, and testing condition (i.e., strain rate and temperature).…”