Effects of chemical alternation on damage accumulation in concentrated solid-solution alloys

Mohammad W Ullah,William J Weber,Haizhou Xue,Ke Jin,Yanwen Zhang,Gihan Velisa,Hongbin Bei

doi:10.1038/s41598-017-04541-8

Abstract

Single-phase concentrated solid-solution alloys (SP-CSAs) have recently gained unprecedented attention due to their promising properties. To understand effects of alloying elements on irradiation-induced defect production, recombination and evolution, an integrated study of ion irradiation, ion beam analysis and atomistic simulations are carried out on a unique set of model crystals with increasing chemical complexity, from pure Ni to Ni80Fe20, Ni50Fe50, and Ni80Cr20 binaries, and to a more complex Ni40Fe40Cr20 alloy. Both experimental and simulation results suggest that the binary and ternary alloys exhibit higher radiation resistance than elemental Ni. The modeling work predicts that Ni40Fe40Cr20 has the best radiation tolerance, with the number of surviving Frenkel pairs being factors of 2.0 and 1.4 lower than pure Ni and the 80:20 binary alloys, respectively. While the reduced defect mobility in SP-CSAs is identified as a general mechanism leading to slower growth of large defect clusters, the effect of specific alloying elements on suppression of damage accumulation is clearly demonstrated. This work suggests that concentrated solid-solution provides an effective way to enhance radiation tolerance by creating elemental alternation at the atomic level. The demonstrated chemical effects on defect dynamics may inspire new design principles of radiation-tolerant structural alloys for advanced energy systems.

Highlights

A new direction of research to substantially enhance alloy performance has been stimulated in material science due to the recent success in fabrication of single-phase concentrated solid-solution alloys (SP-CSAs)[1,2,3,4,5]
Damage accumulation due to cumulative irradiation of Ni, Ni80Fe20, Ni80Cr20, Ni50Fe50 and Ni40Fe40Cr20 alloys has been studied in both ion irradiation experiments and molecular dynamics simulations
The single crystals of these alloys have been irradiated with 1.5 MeV Ni or Mn ions at fluences ranging from 1 × 1013 cm−2 to 1 × 1014 cm−2

Summary

Introduction

A new direction of research to substantially enhance alloy performance has been stimulated in material science due to the recent success in fabrication of single-phase concentrated solid-solution alloys (SP-CSAs)[1,2,3,4,5]. According to Gibbs free energy of mixing ΔGmix = ΔHmix − TΔSmix, entropy can stabilize a phase by lowering free energy with higher entropy, provided that enthalpy is constant In these CSAs, the random arrangement of multiple elemental species on a crystalline lattice results in atomic-level elemental alternation that creates disordered local chemical environments. The RIS can provoke phase instability, embrittlement, and stress corrosion cracking issues[12, 19], whereas void swelling can trigger unacceptable dimensional expansion and can lead to degradation of fracture toughness[18, 20] Due to these adverse effects of radiation, austenitic steels are facing new challenges in the applications of generation nuclear reactors. This result is supported by a recent experimental study on irradiation induced defect evolution in Ni and NiFe binary alloys; where at low-fluences, the equiatomic NiFe alloy demonstrated higher radiation resistance than pure Ni24

Methods

Results

Conclusion