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Title: The BCC/B2 morphologies in Al xNiCoFeCr high-entropy alloys

Abstract

Here, the present work primarily investigates the morphological evolution of the body-centered-cubic (BCC)/B2 phases in Al xNiCoFeCr high-entropy alloys (HEAs) with increasing Al content. It is found that the BCC/B2 coherent morphology is closely related to the lattice misfit between these two phases, which is sensitive to Al. There are two types of microscopic BCC/B2 morphologies in this HEA series: one is the weave-like morphology induced by the spinodal decomposition, and the other is the microstructure of a spherical disordered BCC precipitation on the ordered B2 matrix that appears in HEAs with a much higher Al content. The mechanical properties, including the compressive yielding strength and microhardness of the Al xNiCoFeCr HEAs, are also discussed in light of the concept of the valence electron concentration (VEC).

Authors:
 [1];  [1];  [1];  [1];  [1];  [2];  [3];  [3]
  1. Dalian Univ. of Technology, Dalian (China)
  2. The Univ. of Tennessee, Knoxville, TN (United States)
  3. Guilin Univ. of Electronic Technology, Guilin (China)
Publication Date:
Research Org.:
Univ. of Tennessee, Knoxville, TN (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
OSTI Identifier:
1356091
Alternate Identifier(s):
OSTI ID: 1362287
Grant/Contract Number:
FE0008855
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Metals
Additional Journal Information:
Journal Volume: 7; Journal Issue: 2; Journal ID: ISSN 2075-4701
Publisher:
MDPI
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; high-entropy alloys; Al-Ni-Co-Fe-Cr alloys; microstructure; precipitation morphology; mechanical property

Citation Formats

Ma, Yue, Jiang, Beibei, Li, Chunling, Wang, Qing, Dong, Chuang, Liaw, Peter K., Xu, Fen, and Sun, Lixian. The BCC/B2 morphologies in AlxNiCoFeCr high-entropy alloys. United States: N. p., 2017. Web. doi:10.3390/met7020057.
Ma, Yue, Jiang, Beibei, Li, Chunling, Wang, Qing, Dong, Chuang, Liaw, Peter K., Xu, Fen, & Sun, Lixian. The BCC/B2 morphologies in AlxNiCoFeCr high-entropy alloys. United States. doi:10.3390/met7020057.
Ma, Yue, Jiang, Beibei, Li, Chunling, Wang, Qing, Dong, Chuang, Liaw, Peter K., Xu, Fen, and Sun, Lixian. Wed . "The BCC/B2 morphologies in AlxNiCoFeCr high-entropy alloys". United States. doi:10.3390/met7020057. https://www.osti.gov/servlets/purl/1356091.
@article{osti_1356091,
title = {The BCC/B2 morphologies in AlxNiCoFeCr high-entropy alloys},
author = {Ma, Yue and Jiang, Beibei and Li, Chunling and Wang, Qing and Dong, Chuang and Liaw, Peter K. and Xu, Fen and Sun, Lixian},
abstractNote = {Here, the present work primarily investigates the morphological evolution of the body-centered-cubic (BCC)/B2 phases in AlxNiCoFeCr high-entropy alloys (HEAs) with increasing Al content. It is found that the BCC/B2 coherent morphology is closely related to the lattice misfit between these two phases, which is sensitive to Al. There are two types of microscopic BCC/B2 morphologies in this HEA series: one is the weave-like morphology induced by the spinodal decomposition, and the other is the microstructure of a spherical disordered BCC precipitation on the ordered B2 matrix that appears in HEAs with a much higher Al content. The mechanical properties, including the compressive yielding strength and microhardness of the AlxNiCoFeCr HEAs, are also discussed in light of the concept of the valence electron concentration (VEC).},
doi = {10.3390/met7020057},
journal = {Metals},
number = 2,
volume = 7,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2017},
month = {Wed Feb 15 00:00:00 EST 2017}
}

Journal Article:
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Cited by: 6works
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  • The present work primarily investigates the morphological evolution of the body-centered-cubic (BCC)/B2 phases in AlxNiCoFeCr high-entropy alloys (HEAs) with increasing Al content. It is found that the BCC/B2 coherent morphology is closely related to the lattice misfit between these two phases, which is sensitive to Al. There are two types of microscopic BCC/B2 morphologies in this HEA series: one is the weave-like morphology induced by the spinodal decomposition, and the other is the microstructure of a spherical disordered BCC precipitation on the ordered B2 matrix that appears in HEAs with a much higher Al content. The mechanical properties, including themore » compressive yielding strength and microhardness of the AlxNiCoFeCr HEAs, are also discussed in light of the concept of the valence electron concentration (VEC).« less
  • Cited by 10
  • The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe 36Ni 18Mn 33Al 13Ti x with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σ y, from 270 MPa to 953 MPa, but with a concomitant decrease inmore » ductility from 22% elongation to 2.3%. Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe 36Ni 18Mn 33Al 13Ti 4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.« less
  • A series of AlCrCoNiFe based alloys with equal percentage of principal components (high-entropy alloys or HE alloys) is fabricated. The related crystalline structures of the alloys are measured and calculated. Results show that the formed bcc phase is a compound based B2 structure where there is partial ionic bonding between Al and other transition metals. Thus, the bcc structure of the alloys should be a B2 instead of an A2 due to the large difference in electronegativities among the components consisting of the HE alloys.
  • In present study, structure and mechanical properties of the Al{sub x}CrNbTiVZr (x = 0; 0.25; 0.5; 1) high-entropy alloys after arc melting and annealing at 1200 °C for 24 h are investigated. The CrNbTiVZr alloy is composed of body centered cubic (bcc) and C15 (face centered cubic) Laves phases while the Al{sub x}CrNbTiVZr (x = 0.25; 0.5; 1) alloys consist of bcc and two C14 (hexagonal close packed) Laves phases with different chemical compositions. Thermodynamic modeling predicts existence of two phases – bcc and C15 Laves phase and broadening of single bcc phase field due to Al addition. The densitymore » of the alloys decreases with the increase of Al content. The alloys are found to be extremely brittle at room temperature and 600 °C. The alloys have high strength at temperatures of 800–1000 °C. For example, yield strength at 800 °C increases from 440 MPa for the CrNbTiVZr alloy to 1250 MPa for the AlCrNbTiVZr alloy. The experimental phase composition of the Al{sub x}CrNbTiVZr alloys is compared with predicted equilibrium phases and the factors governing the transformation of C15 to C14 Laves phases due to Al addition to the CrNbTiVZr alloy analyzed. Specific properties of the alloys are compared with other high-entropy alloys and commercial Ni-based superalloys. - Highlights: •Al{sub x}CrNbTiVZr (x = 0; 0.25; 0.5; 1) alloys are arc melted and annealed at 1200 °C. •The CrNbTiVZr alloy has bcc and C15 Laves phases. •The Al-containing alloys are composed of bcc and two C14 Laves phases. •The alloys demonstrate high specific strength at temperatures of 800 °C and 1000 °C. •The strength of the alloys increases in proportion with increase of Al content.« less