Microstructural features underpinning the mechanical behavior of powder metallurgy Cr-based alloys

Bryan Lim; Chris M. Fancher; Jeffrey M. Brookins; Selda Nayir; Jonathan D. Poplawsky; Matthew G. Boebinger; Marissa C. Brennan; Steve Buresh; Michael Spencer; Brian Gordon; Peeyush Nandwana

doi:10.1016/j.jallcom.2025.179172

Microstructural features underpinning the mechanical behavior of powder metallurgy Cr-based alloys

Bryan Lim, Chris M. Fancher, Jeffrey M. Brookins, Selda Nayir, Jonathan D. Poplawsky, Matthew G. Boebinger, Marissa C. Brennan, Steve Buresh, Michael Spencer, Brian Gordon, Peeyush Nandwana

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

Abstract

Refractory materials such as Cr-based alloys offer the potential of enhanced elevated temperature performance but have been limited by their poor formability. However, powder metallurgy has been shown to be a viable pathway to fabricate these alloys. Nanophase separation sintering (NPSS) in particular has been used in the literature to accelerate the densification of powder metallurgy Cr- and W-based alloys. Here, we explore microstructure evolution during NPSS in a binary Cr₈₅Ni₁₅ alloy consolidated via (i) cold pressing & pressureless sintering and (ii) hot isostatic pressing followed by hot extrusion & hot upsetting, and the role of these different processing routes on resulting material properties. The alloy lacked room temperature tensile ductility regardless of consolidation process, with multi-length scale characterization, including scanning electron microscopy, transmission electron microscopy, atom probe tomography, X-ray diffraction, and uniaxial tensile testing, revealing that brittleness was due to intrinsically poor Cr grain boundary cohesion. Tensile testing conducted at 760 °C showed marked strength reduction for the extruded & upset (94 %) condition compared to the pressed & sintered (18 %). The formation of orthorhombic CrNi₂ intermetallics functioned as precipitate strengtheners and prevented elevated temperature softening in the pressed and sintered condition. The findings offer foundational insights into aiding the future development of Cr-based alloys.

Original language	English
Article number	179172
Journal	Journal of Alloys and Compounds
Volume	1020
DOIs	https://doi.org/10.1016/j.jallcom.2025.179172
State	Published - Mar 15 2025

Funding

This research was supported by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), Advanced Materials and Manufacturing Technologies Office (AMMTO) under Contract Number DE-AC05\u201300OR22725 with UT-Battelle LLC and Award Number DE-EE0009115. A portion of the research was conducted at the Manufacturing Demonstration Facility, a DOE Office of Science user facility at Oak Ridge National Laboratory. S/TEM and APT research was supported by the Center for Nanophase Materials Sciences, also a DOE Office of Science user facility at Oak Ridge National Laboratory, under proposal CNMS2024-A-02257. Jefferey Baxter, James Burns, Kelsey H. Epps, Sarah H. Graham, and Andres Marquez-Rossy (Oak Ridge National Laboratory) are all acknowledged for their technical assistance. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).

Keywords

Chromium
Mechanical properties
Microstructure
Powder metallurgy
Tensile test

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10.1016/j.jallcom.2025.179172

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title = "Microstructural features underpinning the mechanical behavior of powder metallurgy Cr-based alloys",

abstract = "Refractory materials such as Cr-based alloys offer the potential of enhanced elevated temperature performance but have been limited by their poor formability. However, powder metallurgy has been shown to be a viable pathway to fabricate these alloys. Nanophase separation sintering (NPSS) in particular has been used in the literature to accelerate the densification of powder metallurgy Cr- and W-based alloys. Here, we explore microstructure evolution during NPSS in a binary Cr85Ni15 alloy consolidated via (i) cold pressing \& pressureless sintering and (ii) hot isostatic pressing followed by hot extrusion \& hot upsetting, and the role of these different processing routes on resulting material properties. The alloy lacked room temperature tensile ductility regardless of consolidation process, with multi-length scale characterization, including scanning electron microscopy, transmission electron microscopy, atom probe tomography, X-ray diffraction, and uniaxial tensile testing, revealing that brittleness was due to intrinsically poor Cr grain boundary cohesion. Tensile testing conducted at 760 °C showed marked strength reduction for the extruded \& upset (94 \%) condition compared to the pressed \& sintered (18 \%). The formation of orthorhombic CrNi2 intermetallics functioned as precipitate strengtheners and prevented elevated temperature softening in the pressed and sintered condition. The findings offer foundational insights into aiding the future development of Cr-based alloys.",

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author = "Bryan Lim and Fancher, \{Chris M.\} and Brookins, \{Jeffrey M.\} and Selda Nayir and Poplawsky, \{Jonathan D.\} and Boebinger, \{Matthew G.\} and Brennan, \{Marissa C.\} and Steve Buresh and Michael Spencer and Brian Gordon and Peeyush Nandwana",

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AU - Lim, Bryan

AU - Fancher, Chris M.

AU - Brookins, Jeffrey M.

AU - Nayir, Selda

AU - Poplawsky, Jonathan D.

AU - Boebinger, Matthew G.

AU - Brennan, Marissa C.

AU - Buresh, Steve

AU - Spencer, Michael

AU - Gordon, Brian

AU - Nandwana, Peeyush

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AB - Refractory materials such as Cr-based alloys offer the potential of enhanced elevated temperature performance but have been limited by their poor formability. However, powder metallurgy has been shown to be a viable pathway to fabricate these alloys. Nanophase separation sintering (NPSS) in particular has been used in the literature to accelerate the densification of powder metallurgy Cr- and W-based alloys. Here, we explore microstructure evolution during NPSS in a binary Cr85Ni15 alloy consolidated via (i) cold pressing & pressureless sintering and (ii) hot isostatic pressing followed by hot extrusion & hot upsetting, and the role of these different processing routes on resulting material properties. The alloy lacked room temperature tensile ductility regardless of consolidation process, with multi-length scale characterization, including scanning electron microscopy, transmission electron microscopy, atom probe tomography, X-ray diffraction, and uniaxial tensile testing, revealing that brittleness was due to intrinsically poor Cr grain boundary cohesion. Tensile testing conducted at 760 °C showed marked strength reduction for the extruded & upset (94 %) condition compared to the pressed & sintered (18 %). The formation of orthorhombic CrNi2 intermetallics functioned as precipitate strengtheners and prevented elevated temperature softening in the pressed and sintered condition. The findings offer foundational insights into aiding the future development of Cr-based alloys.

KW - Chromium

KW - Mechanical properties

KW - Microstructure

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Microstructural features underpinning the mechanical behavior of powder metallurgy Cr-based alloys

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Keywords

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