Title: Additive manufacturing of a metastable high entropy alloy: Metastability engineered microstructural control via process variable driven elemental segregation

Abstract

Compositional paradigm shift in high entropy alloys (HEAs) provided new opportunities for microstructural engineering, whereas process control during laser powder bed fusion (LPBF) additive manufacturing (AM) enable fine microstructure tailoring. Metastability engineering in transformation induced plasticity (TRIP) HEAs by addition of minor alloying elements is an attractive strategy for fine microstructural tuning. This study explored in detail the microstructural evolution during LPBF AM of a metastable Fe₄₀Mn₂₀Co₂₀Cr₁₅Si₅ (at.%) dual phase HEA (CS-HEA). LPBF processing window for CS-HEA was established based on quantitative analysis and experiments. Based on melt pool overlap lack of fusion pores were observed at lower energy densities (J) of $$\textit{J}$$ ≤ 31.25 J/mm³ and key-hole formation by melt pool destabilization in case of $$\textit{J}$$ ≥ 75 J/mm³. The microstructure of CS-HEA consists of metastable FCC-γ and HCP-ε phases; LPBF process parameters governed the final phase fraction in the alloy which has been correlated to metastability alteration of the high temperature γ phase. Final microstructural engineering was devised by LPBF process control which enabled cooling rate manipulation to guide Mn and Si segregation at the cell boundaries, thereby controlling the matrix metastability and final phase fraction. Additionally, high resolution transmission electron microscopy (TEM) revealed disparity in stacking fault morphology in CS-HEA with LPBF process variable alterations associated with local variations in chemical composition and stacking fault energy. Further, the phase evolution with process parameters also affected the nanomechanical behavior of the alloy.

Authors:

Agrawal, Priyanshi  ^[1];

• Search DOE PAGES for author "Agrawal, Priyanshi"
• Search DOE PAGES for ORCID "0000-0001-5937-1023"

Thapliyal, Saket  ^[1];

• Search DOE PAGES for author "Thapliyal, Saket"
• Search DOE PAGES for ORCID "0000-0001-6241-5904"

Agrawal, Priyanka  ^[2];

• Search DOE PAGES for author "Agrawal, Priyanka"
• Search DOE PAGES for ORCID "0000-0001-9894-9625"

Dhal, Abhijeet  ^[2];

• Search DOE PAGES for author "Dhal, Abhijeet"
• Search DOE PAGES for ORCID "0000-0001-9401-649X"

Haridas, Ravi Sankar  ^[2];

• Search DOE PAGES for author "Haridas, Ravi Sankar"
• Search DOE PAGES for ORCID "0000-0002-6552-2630"

Gupta, Sanya ^[2]; Mishra, Rajiv S.  ^[2]

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

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+ Show Author Affiliations

1. Univ. of North Texas, Denton, TX (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Univ. of North Texas, Denton, TX (United States)

Publication Date:

Wed Mar 22 00:00:00 EDT 2023

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1969809

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing

Additional Journal Information:

Journal Volume: 872; Journal ID: ISSN 0921-5093

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Additive manufacturing; Solidification; High entropy alloy; Microstructural characterization; Transformation induced plasticity