EFFECT OF STRAIN PATH ON MICROSTRUCTURE AND MECHANICAL PROPERTIES IN COLD - ROLLED [FeNi]69Cr15Mn10Nb6 HIGH - ENTROPY ALLOY

Abstract

[FeNi]₆₉Cr₁₅Mn₁₀Nb₆ high - entropy alloys (HEAs) were subjected to heavy cold-rolling process at ambient temperature through two distinct routes, namely unidirectional cold-rolling (UCR) and multistep cross cold-rolling (MSCCR) routes, to investigate the effect of the strain path on the microstructure and mechanical properties of the alloys. In the MSCCR route, the specimen rotated 90° around the normal direction axis between each cycle. The as-homogenized specimen revealed a two-phase microstructure consisting of FeNiNb - rich dendrites distributed in a nearly homogenous face-centered cubic (FCC) HEA matrix. Here, FeNiNb - rich dendrites were elongated,
broken down, and stretched along the rolling direction during both processing routes. In the MSCCR - processed specimen, the dendrites exhibited a smaller average size with a more uniform distribution compared to that of the UCR specimen, which could be mainly ascribed to the elongation mechanisms in the normal and transverse directions during the MSCCR route. These microstructural features, introduced through MSCCR, appeared to be most prone to shear band formation and grain refinement. The MSCCR - processed specimen shows a microhardness of 445 HV, a tensile strength of 1245 MPa, and a remarkable elongation of 16 % at ambient temperature, outperforming the UCR-processed specimen with a microhardness of 418 HV, a tensile strength of 1180 MPa, and an elongation of 14 %. The superior mechanical properties of the MSCCR - processed specimen are attributed to its refined microstructure,
increased dislocation density, and uniform distribution of FeNiNb - rich dendrites within the microstructure.