A critical evaluation of microstructure-texture-mechanical behavior heterogeneity in high pressure torsion processed CoCuFeMnNi high entropy alloy

Abstract

The present study aims to understand the evolution of textural and microstructural heterogeneity and its effect on evolution of mechanical properties of an equiatomic FCC CoCuFeMnNi high entropy alloy (HEA) disc subjected to high pressure torsion (HPT). HPT was performed on disc specimen with a hydrostatic pressure of 5 GPa for 0.1, 0.5, 1 and 5 turns at room temperature diffraction analysis shows decrease in crystalline size with simultaneous increase in dislocation density for five-turn HPT sample with increasing strain from centre to the periphery of the disc.Microstructural analysis using electron back scatter diffraction and transmission electron microscopy indicates extensive grain fragmentation (≈ 55 nm at the periphery of five-turn sample). The evolution of hardness from centre to the periphery of the disc cannot be explained only on the basis of evolution of grain size and dislocation density. The increase in contribution from solid solution strengthening due to partial dissolution of copper rich nano-clusters is expected to be the underlying cause for increase in the hardness. Thus, evolution of gradient microstructure, texture, and chemistry opens up new vistas for designing functionally graded materials for engineering materials.

Texture evolution in high-pressure torsion processing

“…Limited investigations are available dealing with the texture prediction during HPT processing for FCC [116,126,136,262] and BCC [188] metals and there are no similar investigations for HCP materials. For single crystal FCC metals, the texture evolution for Ni and Al after HPT processing was predicted using a crystal plasticity finite element (CPFEM) model and the results are in good agreement with the experiments [126,262].…”

“…3: domination of Cube ε eq = 22.6-113: presence of A and B fibers and weak C [128] Pure Cu and Cu matrix composite P= 3 GPa, V = 0.2 rpm, RT N = 2, 4 and 6 turns XRD at the mid-radius and edge of the discs Composite ε eq = 14.5-23.3: gradual formation of A and B fibers with the domination of B/ ε eq = 46.7-72.5: texture weakening Pure Cu ε eq = 29: presence of full of A and B fibers at r = 3 mm from the center of the disc Annealed at 1273 K for 384h presence of A and B fibers with domination of and B/ Cu-Ni-Si P= 6 GPa, V = 1 rpm, RT N = 1/2, 1, 5 and 10 turns EBSD at the center, mid-radius and edge of the discs ε eq = 0.45-5.66: gradual formation of A and B fibers ε eq = 11.3-56.65: stable texture ε eq = 101-203: A-fiber with the domination of [72] Cu/Nb composite P = 4.5GPa, V = 1.2rpm, RT N = 50°, 210°, 5 turns and 20 turns XRD measurement a cross the radii of the discs Cu layer ε eq = 2.42-6.23: near-random texture ε eq = 10.8-165.1: complete A-fiber ε eq = 1437-2592: domination of [131] Fe-Ni P= 6 GPa, V = 1 rpm, RT and 523 K N = 1/2, 1, 5 and 10 turns EBSD at the mid-radius of the discs At RT ε eq = 5.66-56.6: presence of all shear components with the domination of B ε eq = 113.3: stable texture At 523 K ε eq = 5.66:-113.3: weakening of the texture but the presence of C [54] Fe-based shape memory P = 8 GPa, RT, N = 2 turns synchrotron XRD at the mid-radius of the disc ε eq = 9.06: presence of C [132]Pd-Au P= 4.5 GPa, V = π/2 per 18 s -1 , RT N = 1/2 turn synchrotron XRD at the mid-radius of the discs Initial nano-grain ε eq = 7.67: presence of and Cube Initial coarse-grain ε eq = 7.67: typical shear texture (weak A-fiber, strong B-fiber with C domination)[133] Pd-Au P= 6 GPa, V = 6°s -1 , RT N = 7, 36 and 104° rotation angle XRD at the edge of the discs ε eq = 0-0.4: near-random texture ε eq = 0.57-1.61: formation of , B/ and C ε eq = 2.42-9.69: domination of B/ XRD at the mid-radius and the edge of the discs ε eq = 9.23-75: presence of , and strong B/ , RT, N = 5 turns synchrotron XRD across the whole radius of the discs ε eq = 0-22.6: gradual formation of shear texture ε eq = 45.3-67.9: typical shear texture with the domination of A and ε eq = 90.6: texture weakening[136] …”

In Situ Neutron Diffraction Investigating Microstructure and Texture Evolution upon Heating of Nanostructured CoCrFeNi High‐Entropy Alloy

“…It is consistent with similar studies on the same material [ 38 ] and with typical shear textures in fcc metals processed by HPT, such as pure Al, [ 60 ] an fcc CrMnFeCoNi, [ 61 ] and an fcc CoCuFeMnNi. [ 62 ] For the texture after heating at 950 K as depicted in Figure 6c, the anterior γ –<111> fiber retains in Bank 1 but weakened as Banks 2 and 3 also show apparently high 111 intensity. This observation can be explained in two parts.…”

Recent Advances in Additive Manufacturing of High Entropy Alloys and Their Nuclear and Wear-Resistant Applications

“…Zhang et al [128] reviewed high pressure induced phase transitions in HEAs. Application of high pressure torsion [37,[129][130][131][132][133][134][135][136][137][138][139][140][141][142] is more frequent than other pressure techniques [136,[143][144][145][146][147][148][149][150].…”