Unveiling the interplay of deformation mechanisms in a metastable high entropy alloy with tuned composition using synchrotron X-ray diffraction

E Polatidis,S Shukla,J Čapek,S Van Petegem,N Casati,R.S Mishra

doi:10.1016/j.mtcomm.2022.103155

Abstract

The mechanical behavior of a metastable high entropy alloy (HEA) with composition Fe39-Mn20-Co20-Cr15-Si5-1Al at% is investigated. The deformation mechanisms contributing to its mechanical properties are unveiled, by performing uniaxial tensile tests in situ with synchrotron X-ray diffraction. Three distinct deformation regimes are detected. The initial elastic and early dislocation-based plasticity deformation is followed by a moderate work hardening rate regime, which is associated with the deformation-induced phase formation of ε-martensite, with hexagonal close-packed (hcp) crystal structure as well as slip in the parent austenitic phase. During the third deformation regime, the phase transformation continues to occur in combination with 2 modes of hcp twinning as well as slip in the unfavorably oriented grains for twinning. The interplay of all these co-existing deformation mechanisms can be evidenced by synchrotron X-ray diffraction.

Highlights

High Entropy alloys (HEAs) were first introduced in 2004 [1,2] as alloys having at least five principal elements in or near equi-atomic compositions
A HEA with a nominal composition of Fe39-Mn20-Co20-Cr15-Si5Al1 was produced by vacuum arc casting in a cold copper cruci ble with a size of 300 × 100 × 6 mm3 in Ar atmosphere
In situ deformation and synchrotron X-ray diffraction in transmission geometry can reveal the characteristics of the interplay of deformation mechanisms in a Fe39-Mn20-Co20-Cr15-Si5-Al1 HEA

Summary

Introduction

High Entropy alloys (HEAs) were first introduced in 2004 [1,2] as alloys having at least five principal elements in or near equi-atomic compositions. The rationale behind the HEA design concept is the usu ally high entropy of mixing. Based on the equimolar alloy designed by Cantor et al [2], variants with modified compositions or non-equimolar compositions have been developed, to reduce the stacking fault energy of the system and promote twinning induced plasticity (TWIP) and/or the transformation-induced plasticity (TRIP), the so-called metastable HEAs. Based on the equimolar alloy designed by Cantor et al [2], variants with modified compositions or non-equimolar compositions have been developed, to reduce the stacking fault energy of the system and promote twinning induced plasticity (TWIP) and/or the transformation-induced plasticity (TRIP), the so-called metastable HEAs As such materials with superior mechanical properties have emerged. Another strengthening mechanism for HEAs is the addition of nitrogen via the interstitial strengthening effect [3,4]

Results

Discussion

Conclusion