Model interatomic potentials and lattice strain in a high-entropy alloy
- PDF / 735,792 Bytes
- 8 Pages / 584.957 x 782.986 pts Page_size
- 0 Downloads / 224 Views
ARTICLE Model interatomic potentials and lattice strain in a high-entropy alloy Diana Farkasa) Department of Materials Science and Engineering, Virginia Tech, Blacksburg, Virginia 24061, USA
Alfredo Caro Science and Technology Campus, George Washington University, Ashburn, Virginia 20147, USA (Received 28 February 2018; accepted 27 June 2018)
A set of embedded atom method model interatomic potentials is presented to represent a highentropy alloy with five components. The set is developed to resemble but not model precisely face-centered cubic (fcc) near-equiatomic mixtures of Fe–Ni–Cr–Co–Cu. The individual components have atomic sizes deviating up to 3%. With the heats of mixing of all binary equiatomic random fcc mixtures being less than 0.7 kJ/mol and the corresponding value for the quinary being 0.0002 kJ/mol, the potentials predict the random equiatomic fcc quinary mixture to be stable with respect to phase separation or ordering and with respect to bcc and hcp random mixtures. The details of lattice distortion, strain, and stress states in this phase are reported. The standard deviation in the individual nearest neighbor bond lengths was found to be in the range of 2%. Most importantly, individual atoms in the alloy were found to be under atomic strains up to 0.5%, corresponding to individual atomic stresses up to several GPa.
I. INTRODUCTION
The conventional alloy design strategy is commonly based on one element as the principal constituent with other alloying elements added in minor concentrations for the optimization of various properties. In recent years, a new alloy design concept has been introduced, based on several principal elements in equiatomic or nearequiatomic compositions.1,2 Due to the effects of high entropy of mixing and low heat of mixing, these new alloys can form a random solid solution in a single-phase structure (fcc or bcc) instead of ordered intermetallic compounds or decomposition into different phases.3,4 The design of high-entropy alloys (HEAs) requires a radical departure from conventional notions of alloy design. The high mixing entropy enhances the formation of solution-type phases by lowering the free energy of the disordered phase, and in general leads to a simple microstructure.5,6 “HEAs” were named as such because of this effect in 2004.5,7 As pointed out in recent reviews,2–4 this concept is beyond the conventional scope of materials design and introduces a new path of developing advanced materials with unique properties, which cannot be achieved by the conventional micro-alloying approach based on only one dominant element. Many HEAs with promising properties have been reported in the literature.2 Mechanical properties are particularly interesting, with attractive combinations of strength and ductility. For example,8 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2018.245 J. Mater. Res., 2018
a high-entropy Fe–Co–Ni–Cr–Mn alloy with a single face-centered cubic (fcc) phase was synthesized and subsequently annealed at different temper
Data Loading...
