Microstructure and Mechanical Properties Evolution of the Al, C-Containing CoCrFeNiMn-Type High-Entropy Alloy during Cold Rolling

Abstract

The effect of cold rolling on the microstructure and mechanical properties of an Al- and C-containing CoCrFeNiMn-type high-entropy alloy was reported. The alloy with a chemical composition (at %) of (20–23) Co, Cr, Fe, and Ni; 8.82 Mn; 3.37 Al; and 0.69 C was produced by self-propagating high-temperature synthesis with subsequent induction. In the initial as-cast condition the alloy had an face centered cubic single-phase coarse-grained structure. Microstructure evolution was mostly associated with either planar dislocation glide at relatively low deformation during rolling (up to 20%) or deformation twinning and shear banding at higher strain. After 80% reduction, a heavily deformed twinned/subgrained structure was observed. A comparison with the equiatomic CoCrFeNiMn alloy revealed higher dislocation density at all stages of cold rolling and later onset of deformation twinning that was attributed to a stacking fault energy increase in the program alloy; this assumption was confirmed by calculations. In the initial as-cast condition the alloy had low yield strength of 210 MPa with yet very high uniform elongation of 74%. After 80% rolling, yield strength approached 1310 MPa while uniform elongation decreased to 1.3%. Substructure strengthening was found to be dominated at low rolling reductions (<40%), while grain (twin) boundary strengthening prevailed at higher strains.

Recrystallized microstructures and mechanical properties of a C-containing CoCrFeNiMn-type high-entropy alloy

“…14a. After the solidification, the alloy is expected to have an fcc single phase structure, that is consistent with an experimentally obtained as-cast microstructure [39] and the program alloy structure after cold rolling (Fig. 1).…”

“…In addition, carbon can change the contributions of operating deformation mechanisms due to stackingfault energy (SFE) changing. It should be noted, however, that different sources claim both increase [44][45][46] and decrease [9,38,39] of the twinning intensity with the change of SFE. Much smaller attention has been paid so far to precipitation hardening of HEAs by fine carbide particles.…”

“…Meanwhile, interstitial alloying with elements like carbon can efficiently increase the strength of 3d transition metal fcc HEAs without considerable loss in ductility; mostly due to a strong solid-solution strengthening effect [9,[35][36][37][38][39][40][41][42][43][44][45]. In addition, carbon can change the contributions of operating deformation mechanisms due to stackingfault energy (SFE) changing.…”

From High-Manganese Steels to Advanced High-Entropy Alloys

“…On the other hand, C-Mn short range ordered clusters contribute to the splitting of partial dislocations and ease the onset of deformation twinning [26]. In turn, in the C-free HEA, a more prolonged stage of deformation by dislocation slip retards the initiation of deformation twinning and delays the formation sequence of twin-matrix lamellae, their rotation into the rolling plane, and the subsequent onset of shear banding [27][28][29][30][31][32][33], which are thus shifted to higher strains. Hence, the related formation of a pronounced Brass-type texture with the typical texture components-Brass, Goss, CuT and γ-fiber-is shifted to higher degrees of thickness reduction during rolling of the HEA.…”

Mechanical Properties and Corrosion Resistance of NbTiAlSiZrNx High-Entropy Films Prepared by RF Magnetron Sputtering

“…The oxide can improve the tensile strength of CrMnFeCoNi HEAs [19]. Besides composition, fabrication methods can also affect the microstructure and mechanical properties of HEAs [20,21]. Magnetron sputtering and laser cladding are two of the most important methods for preparing HEA coatings [22][23][24][25][26][27][28].…”