Processing-Microstructure-Tensile Performance Nexus in Pure Molybdenum

Research output: Contribution to journalConference articlepeer-review

Abstract

The accelerator-based method for producing 99Mo, the parent isotope of 99mTc, involves accelerating an electron beam at an aMo target to knock off a neutron to make 99Mo. Powder metallurgy processing can be performed by using the press-and-sintering method on the feedstock aMo powder. However, the typically observed low ductility at RT of powder metallurgy Mo raises concerns about the integrity of the aMo targets during start-up and continuous operation under the accelerator beam. This paper details the tensile properties and microstructure of Mo processed by different methods press-and-sintered (before and after a purification process) to that of rolled Mo, which is known to have RT ductility. Not surprisingly, the rolled Mo exhibited the highest strength and best stability in ductility over the aMo or UHP Mo press-and-sintered material. The aMo material had higher strength than the UHP material but no RT ductility. Ductility was observed at lower temperatures in the UHP material but at lower strengths than aMo, which is most likely due to its relatively large grain size compared with aMo. The fracture surfaces of the UHP Mo material tested at RT exhibited some dimpling, which is indicative of some ductile fracture. At RT, the fracture surface of the aMo material was rather flat, finding lots of voids and defects in the microstructure after tensile testing. The grain structure was smaller in the aMo material, giving it higher strength, but the microstructure was conducive to cavity formation, whereas not as many voids were found in the UHP Mo microstructure. This result suggests a delicate interplay between impurity levels and grain structure in determining the mechanical properties of Mo for target applications. This work will elucidate the mechanisms that influence the microstructure formed in each processing method of Mo. Emphasis will be placed on understanding the role of impurities and deformation in the microstructure to better understand the mechanism that allows for rolled Mo to have the highest strength-ductility synergy.

Original languageEnglish
Pages (from-to)578-581
Number of pages4
JournalTransactions of the American Nuclear Society
Volume131
Issue number1
DOIs
StatePublished - 2024
Event2024 Transactions of the American Nuclear Society on Winter Conference and Expo, ANS 2024 - Orlando, United States
Duration: Nov 17 2024Nov 21 2024

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