An engineering perspective on evaluating mechanisms governing ductility in pure molybdenum

Holden C. Hyer; Sebastien Dryepondt; Thomas R. Muth; Jim Nash

doi:10.1557/s43578-025-01672-x

An engineering perspective on evaluating mechanisms governing ductility in pure molybdenum

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

Abstract

The United States lacks a stable domestic supply of ⁹⁹mTc, a critical medical imaging isotope generated from ⁹⁹Mo. Accelerator-based production using ¹⁰⁰Mo targets (aMo) introduces mechanical concerns due to the ductile-to-brittle transition temperature inherent to refractory metals like Mo. This study evaluates the tensile behavior of aMo targets from 25 to 1000 °C, compared to powder-metallurgy-processed natural Mo (PMo) and cast-and-rolled Mo (RMo), both as-received and after 5 ppm O₂ exposure in flowing He. RMo showed superior ductility (7.3% at 25 °C, 48% at 1000 °C) and strength, attributed to its fine, elongated grains and high geometrically necessary dislocation density. PMo exhibited variable ductility (up to 33%), while aMo remained brittle, with a maximum elongation of 10.4% at 600 °C. EBSD analysis revealed weak texture in PMo and aMo, but high defect density in aMo limited dislocation mobility. This work links processing, microstructure, and deformation mechanisms to guide fabrication of ductile refractory targets.

Original language	English
Pages (from-to)	114-140
Number of pages	27
Journal	Journal of Materials Research
Volume	41
Issue number	1
DOIs	https://doi.org/10.1557/s43578-025-01672-x
State	Published - Jan 14 2026

Funding

Support for this work was provided by the US Department of Energy’s National Nuclear Security Administration, Office of Material Management and Minimization’s Molybdenum-99 Program. The aMo and PMo materials were provided by Northstar Medical Radioisotopes. The authors thank Alex Ulrich, Nikhil Valluvan, Donald Nell, and Tomas Montenegro at Northstar and Marc Schrier at Calchemist for their collaboration in this work. Additionally, the authors thank Dr. Katherine Montoya and Mr. Wesley Jones for their thoughtful insights in reviewing the draft manuscript. This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE 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

Dislocations
Mo
Nuclear materials
Oxidation
Stress/strain relationship

Access to Document

10.1557/s43578-025-01672-x

Cite this

@article{e64b5d6819b344cbb7916b67208f3ec9,

title = "An engineering perspective on evaluating mechanisms governing ductility in pure molybdenum",

abstract = "The United States lacks a stable domestic supply of 99mTc, a critical medical imaging isotope generated from 99Mo. Accelerator-based production using 100Mo targets (aMo) introduces mechanical concerns due to the ductile-to-brittle transition temperature inherent to refractory metals like Mo. This study evaluates the tensile behavior of aMo targets from 25 to 1000 °C, compared to powder-metallurgy-processed natural Mo (PMo) and cast-and-rolled Mo (RMo), both as-received and after 5 ppm O2 exposure in flowing He. RMo showed superior ductility (7.3\% at 25 °C, 48\% at 1000 °C) and strength, attributed to its fine, elongated grains and high geometrically necessary dislocation density. PMo exhibited variable ductility (up to 33\%), while aMo remained brittle, with a maximum elongation of 10.4\% at 600 °C. EBSD analysis revealed weak texture in PMo and aMo, but high defect density in aMo limited dislocation mobility. This work links processing, microstructure, and deformation mechanisms to guide fabrication of ductile refractory targets.",

keywords = "Dislocations, Mo, Nuclear materials, Oxidation, Stress/strain relationship",

author = "Hyer, \{Holden C.\} and Sebastien Dryepondt and Muth, \{Thomas R.\} and Jim Nash",

note = "Publisher Copyright: {\textcopyright} UT-Battelle, LLC 2025.",

year = "2026",

month = jan,

day = "14",

doi = "10.1557/s43578-025-01672-x",

language = "English",

volume = "41",

pages = "114--140",

journal = "Journal of Materials Research",

issn = "0884-2914",

publisher = "Springer",

number = "1",

}

TY - JOUR

T1 - An engineering perspective on evaluating mechanisms governing ductility in pure molybdenum

AU - Hyer, Holden C.

AU - Dryepondt, Sebastien

AU - Muth, Thomas R.

AU - Nash, Jim

N1 - Publisher Copyright: © UT-Battelle, LLC 2025.

PY - 2026/1/14

Y1 - 2026/1/14

N2 - The United States lacks a stable domestic supply of 99mTc, a critical medical imaging isotope generated from 99Mo. Accelerator-based production using 100Mo targets (aMo) introduces mechanical concerns due to the ductile-to-brittle transition temperature inherent to refractory metals like Mo. This study evaluates the tensile behavior of aMo targets from 25 to 1000 °C, compared to powder-metallurgy-processed natural Mo (PMo) and cast-and-rolled Mo (RMo), both as-received and after 5 ppm O2 exposure in flowing He. RMo showed superior ductility (7.3% at 25 °C, 48% at 1000 °C) and strength, attributed to its fine, elongated grains and high geometrically necessary dislocation density. PMo exhibited variable ductility (up to 33%), while aMo remained brittle, with a maximum elongation of 10.4% at 600 °C. EBSD analysis revealed weak texture in PMo and aMo, but high defect density in aMo limited dislocation mobility. This work links processing, microstructure, and deformation mechanisms to guide fabrication of ductile refractory targets.

AB - The United States lacks a stable domestic supply of 99mTc, a critical medical imaging isotope generated from 99Mo. Accelerator-based production using 100Mo targets (aMo) introduces mechanical concerns due to the ductile-to-brittle transition temperature inherent to refractory metals like Mo. This study evaluates the tensile behavior of aMo targets from 25 to 1000 °C, compared to powder-metallurgy-processed natural Mo (PMo) and cast-and-rolled Mo (RMo), both as-received and after 5 ppm O2 exposure in flowing He. RMo showed superior ductility (7.3% at 25 °C, 48% at 1000 °C) and strength, attributed to its fine, elongated grains and high geometrically necessary dislocation density. PMo exhibited variable ductility (up to 33%), while aMo remained brittle, with a maximum elongation of 10.4% at 600 °C. EBSD analysis revealed weak texture in PMo and aMo, but high defect density in aMo limited dislocation mobility. This work links processing, microstructure, and deformation mechanisms to guide fabrication of ductile refractory targets.

KW - Dislocations

KW - Mo

KW - Nuclear materials

KW - Oxidation

KW - Stress/strain relationship

UR - https://www.scopus.com/pages/publications/105013776085

U2 - 10.1557/s43578-025-01672-x

DO - 10.1557/s43578-025-01672-x

M3 - Article

AN - SCOPUS:105013776085

SN - 0884-2914

VL - 41

SP - 114

EP - 140

JO - Journal of Materials Research

JF - Journal of Materials Research

IS - 1

ER -

An engineering perspective on evaluating mechanisms governing ductility in pure molybdenum

Abstract

Funding

Keywords

Access to Document

Other files and links

Fingerprint

Cite this