Evolution of microstructure and hardness in Hf25Nb25Ti25Zr25 high-entropy alloy during high-pressure torsion

Jenő Gubicza; Anita Heczel; Megumi Kawasaki; Jae Kyung Han; Yakai Zhao; Yunfei Xue; Shuo Huang; János L. Lábár

doi:10.1016/j.jallcom.2019.02.220

Evolution of microstructure and hardness in Hf₂₅Nb₂₅Ti₂₅Zr₂₅ high-entropy alloy during high-pressure torsion

Jenő Gubicza, Anita Heczel, Megumi Kawasaki, Jae Kyung Han, Yakai Zhao, Yunfei Xue, Shuo Huang, János L. Lábár

Research output: Contribution to journal › Article › peer-review

40 Scopus citations

Abstract

A four-component equimolar high-entropy alloy (HEA) with the composition of HfNbTiZr and body-centered cubic (bcc) structure was processed by HPT at RT. The evolution of the dislocation density, the grain size and the hardness was monitored along the HPT-processed disk radius for different numbers of turns between ¼ and 20. It was found that most of the increase of the dislocation density and the refinement of the grain structure occurred up to the shear strain of ∼40. Between the strains of ∼40 and ∼700, only a slight grain size reduction was observed. The saturated dislocation density and grain size were ∼2.1 × 10¹⁶ m⁻² and ∼30 nm, respectively. The saturation in hardness was obtained at ∼4450 MPa. These values were similar to the parameters determined in the literature for five-component HEAs processed by HPT. The analysis confirmed that the main component in the strength was given by the friction stress in the HPT-processed bcc HfNbTiZr HEA. It was also revealed that the contribution of the high dislocation density to the strength was significantly higher than the effect of the small grain size.

Original language	English
Pages (from-to)	318-328
Number of pages	11
Journal	Journal of Alloys and Compounds
Volume	788
DOIs	https://doi.org/10.1016/j.jallcom.2019.02.220
State	Published - Jun 5 2019
Externally published	Yes

Funding

This work was supported in part by the Ministry of Human Capacities of Hungary within the ELTE University Excellence program (1783-3/2018/FEKUTSRAT); in part by the grant no. VEKOP-2.3.3-15-2016-00002 of the European Structural and Investment Funds; and in part by the National Science Foundation (United States) under Grant No. DMR-1810343. The authors are grateful to Dr. Károly Havancsák for the surface preparation for the EBSD investigations and Mr. Zsolt Maksa for the EBSD experiments. The preparation of the TEM lamellae by Andrea Fenyvesi-Jakab is also acknowledged. This work was supported in part by the Ministry of Human Capacities of Hungary within the ELTE University Excellence program ( 1783-3/2018/FEKUTSRAT ); in part by the grant no. VEKOP-2.3.3-15-2016-00002 of the European Structural and Investment Funds; and in part by the National Science Foundation (United States) under Grant No. DMR-1810343 . The authors are grateful to Dr. Károly Havancsák for the surface preparation for the EBSD investigations and Mr. Zsolt Maksa for the EBSD experiments. The preparation of the TEM lamellae by Andrea Fenyvesi-Jakab is also acknowledged.

Funders	Funder number
Ministry of Human Capacities of Hungary	1783-3/2018/FEKUTSRAT, VEKOP-2.3.3-15-2016-00002
National Science Foundation	1810343, DMR-1810343

Keywords

Dislocations
Hardness
High-entropy alloys
Microstructure
Nanostructured materials
Severe plastic deformation

Access to Document

10.1016/j.jallcom.2019.02.220

Cite this

@article{d207858cd1654da584cd69c562021796,

title = "Evolution of microstructure and hardness in Hf25Nb25Ti25Zr25 high-entropy alloy during high-pressure torsion",

abstract = "A four-component equimolar high-entropy alloy (HEA) with the composition of HfNbTiZr and body-centered cubic (bcc) structure was processed by HPT at RT. The evolution of the dislocation density, the grain size and the hardness was monitored along the HPT-processed disk radius for different numbers of turns between ¼ and 20. It was found that most of the increase of the dislocation density and the refinement of the grain structure occurred up to the shear strain of ∼40. Between the strains of ∼40 and ∼700, only a slight grain size reduction was observed. The saturated dislocation density and grain size were ∼2.1 × 1016 m−2 and ∼30 nm, respectively. The saturation in hardness was obtained at ∼4450 MPa. These values were similar to the parameters determined in the literature for five-component HEAs processed by HPT. The analysis confirmed that the main component in the strength was given by the friction stress in the HPT-processed bcc HfNbTiZr HEA. It was also revealed that the contribution of the high dislocation density to the strength was significantly higher than the effect of the small grain size.",

keywords = "Dislocations, Hardness, High-entropy alloys, Microstructure, Nanostructured materials, Severe plastic deformation",

author = "Jen{\H o} Gubicza and Anita Heczel and Megumi Kawasaki and Han, {Jae Kyung} and Yakai Zhao and Yunfei Xue and Shuo Huang and L{\'a}b{\'a}r, {J{\'a}nos L.}",

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AU - Gubicza, Jenő

AU - Heczel, Anita

AU - Kawasaki, Megumi

AU - Han, Jae Kyung

AU - Zhao, Yakai

AU - Xue, Yunfei

AU - Huang, Shuo

AU - Lábár, János L.

PY - 2019/6/5

Y1 - 2019/6/5

N2 - A four-component equimolar high-entropy alloy (HEA) with the composition of HfNbTiZr and body-centered cubic (bcc) structure was processed by HPT at RT. The evolution of the dislocation density, the grain size and the hardness was monitored along the HPT-processed disk radius for different numbers of turns between ¼ and 20. It was found that most of the increase of the dislocation density and the refinement of the grain structure occurred up to the shear strain of ∼40. Between the strains of ∼40 and ∼700, only a slight grain size reduction was observed. The saturated dislocation density and grain size were ∼2.1 × 1016 m−2 and ∼30 nm, respectively. The saturation in hardness was obtained at ∼4450 MPa. These values were similar to the parameters determined in the literature for five-component HEAs processed by HPT. The analysis confirmed that the main component in the strength was given by the friction stress in the HPT-processed bcc HfNbTiZr HEA. It was also revealed that the contribution of the high dislocation density to the strength was significantly higher than the effect of the small grain size.

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