TY - JOUR
T1 - Processing-Microstructure-Tensile Performance Nexus in Pure Molybdenum
AU - Hyer, Holden C.
AU - Dryepondt, Sebastien
AU - Muth, Thomas R.
AU - Nash, Jim
N1 - Publisher Copyright:
© 2024 American Nuclear Society. All rights reserved.
PY - 2024
Y1 - 2024
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85215584332&partnerID=8YFLogxK
U2 - 10.13182/T131-46051
DO - 10.13182/T131-46051
M3 - Conference article
AN - SCOPUS:85215584332
SN - 0003-018X
VL - 131
SP - 578
EP - 581
JO - Transactions of the American Nuclear Society
JF - Transactions of the American Nuclear Society
IS - 1
T2 - 2024 Transactions of the American Nuclear Society on Winter Conference and Expo, ANS 2024
Y2 - 17 November 2024 through 21 November 2024
ER -