Title: Influence of ordered L1₂ precipitation on strain-rate dependent mechanical behavior in a eutectic high entropy alloy

Abstract

Recent studies indicate that eutectic high-entropy alloys can simultaneously possess high strength and high ductility, which have potential industrial applications. The present study focuses on Al0.7CoCrFeNi, a lamellar dual-phase (fcc?+?B2) precipitation-strengthenable eutectic high entropy alloy. This alloy exhibits an fcc?+?B2 (B2 with bcc nano-precipitates) microstructure resulting in a combination of the soft and ductile fcc phase together with hard B2 phase. Low temperature annealing leads to the precipitation of ordered L12 intermetallic precipitates within the fcc resulting in enhanced strength. The strengthening contribution due to fine scale L12 is modeled using Orowan dislocation bowing and by-pass mechanism. The alloy was tested under quasi-static (strain-rate?=?10-3 s-1) tensile loading and dynamic (strain-rate?=?103 s-1) compressive loading. Due to the fine lamellar microstructure with a large number of fcc-bcc interfaces, the alloy show relatively high flow-stresses, ~1400?MPa under quasi-static loading and in excess of 1800 MPa under dynamic loading. Interestingly, the coherent nano-scale L12 precipitate caused a significant rise in the yield strength, without affecting the strain rate sensitivity (SRS) significantly. These lamellar structures had higher work hardening due to their capability for easily storing higher dislocation densities. The back-stresses from the coherent L12 precipitate were insufficient to cause improvement in twin nucleation, owingmore » to elevated twinning stress under quasi-static testing. However, under the dynamic testing high density of twins were observed.« less

Authors:

Gwalani, Bharat ^[1]; Gangireddy, Sindhura ^[2]; Zheng, Yufeng ^[3]; Soni, Vishal ^[4]; Mishra, Rajiv S.  ^[5];

• Search DOE PAGES for author "Mishra, Rajiv S."
• Search DOE PAGES for ORCID "0000-0002-1699-0614"

Banerjee, Rajarshi ^[5]

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+ Show Author Affiliations

1. Univ. of North Texas, Denton, TX (United States). Advanced Materials and Manufacturing Processes Inst. and Materials Science and Engineering; Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2. Univ. of North Texas, Denton, TX (United States). Advanced Materials and Manufacturing Processes Inst.
3. The Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering
4. Univ. of North Texas, Denton, TX (United States). Materials Science and Engineering
5. Univ. of North Texas, Denton, TX (United States). Advanced Materials and Manufacturing Processes Inst. and Materials Science and Engineering

Publication Date:

Tue Apr 23 00:00:00 EDT 2019

Research Org.:

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1624465

Alternate Identifier(s):

OSTI ID: 1736019

Report Number(s):

PNNL-SA-145678
Journal ID: ISSN 2045-2322; PII: 42870

Grant/Contract Number:  

AC05-76RL01830

Resource Type:

Accepted Manuscript

Journal Name:

Scientific Reports

Additional Journal Information:

Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 2045-2322

Publisher:

Nature Publishing Group

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; 42 ENGINEERING; Science & technology - other topics; Mechanical properties; Metals and alloys