TY - JOUR
T1 - γ+γ′ microstructures in the Co-Ta-V and Co-Nb-V ternary systems
AU - Reyes Tirado, Fernando L.
AU - Perrin Toinin, Jacques
AU - Dunand, David C.
N1 - Funding Information:
This study was supported by the U.S. Department of Commerce , National Institute of Standards and Technology , as part of the Center for Hierarchical Materials Design (CHiMaD) at Northwestern University via award 70NANB14H012 . F.R.T acknowledges the support of a NSF Graduate Research Fellowship . This work made use of the EPIC facility of Northwestern University's NUANCE Center, which has received support by NSF ECCS-1542205 and DMR-1121262 ; and the Materials Characterization and Imaging Facility supported by NSF DMR-1121262 . F.R.T acknowledges experimental assistance from Mr. Ding-Wen Chung, and Ms. Shannon L. Taylor (Northwestern University). Appendix A
Funding Information:
This study was supported by the U.S. Department of Commerce, National Institute of Standards and Technology, as part of the Center for Hierarchical Materials Design (CHiMaD) at Northwestern University via award 70NANB14H012. F.R.T acknowledges the support of a NSF Graduate Research Fellowship. This work made use of the EPIC facility of Northwestern University's NUANCE Center, which has received support by NSF ECCS-1542205 and DMR-1121262; and the Materials Characterization and Imaging Facility supported by NSF DMR-1121262. F.R.T acknowledges experimental assistance from Mr. Ding-Wen Chung, and Ms. Shannon L. Taylor (Northwestern University).
Publisher Copyright:
© 2018 Acta Materialia Inc.
PY - 2018/6/1
Y1 - 2018/6/1
N2 - The Co-Ta-V and Co-Nb-V ternary systems are investigated in a search for L12-ordered γ′ precipitation, based on recent computational predictions of stable γ+γ′ microstructures. Four alloys with nominal (at. %) composition Co-6Ta-6V, Co-5.4Ta-6.6V-xNi (x = 0 and 10), and Co-6Nb-6V are arc-melted, homogenized at 1250 °C, and aged at 900 °C for 2, 16 and 64 h. Nanometric, cuboidal γ′ precipitates within a fcc-γ matrix are discovered in the Co-Ta-V system after aging for 2 h, and in the Co-Nb-V system after cooling from homogenization. The compositions of these two new γ′-phases, as measured via atom probe tomography, are Co3(Ta0.76V0.24) and Co3(Nb0.65V0.35), respectively. Upon aging at 900 °C, the γ′ precipitates coarsen, dissolve and transform to lamellar C36-Co3(Ta,V) and needle-shape D019-Co3(Nb,V), measured as Co3(Nb0.81V0.19) by APT, respectively. This shows that these ternary γ′ phases are metastable and points to the need for their stabilization via additional alloying elements.
AB - The Co-Ta-V and Co-Nb-V ternary systems are investigated in a search for L12-ordered γ′ precipitation, based on recent computational predictions of stable γ+γ′ microstructures. Four alloys with nominal (at. %) composition Co-6Ta-6V, Co-5.4Ta-6.6V-xNi (x = 0 and 10), and Co-6Nb-6V are arc-melted, homogenized at 1250 °C, and aged at 900 °C for 2, 16 and 64 h. Nanometric, cuboidal γ′ precipitates within a fcc-γ matrix are discovered in the Co-Ta-V system after aging for 2 h, and in the Co-Nb-V system after cooling from homogenization. The compositions of these two new γ′-phases, as measured via atom probe tomography, are Co3(Ta0.76V0.24) and Co3(Nb0.65V0.35), respectively. Upon aging at 900 °C, the γ′ precipitates coarsen, dissolve and transform to lamellar C36-Co3(Ta,V) and needle-shape D019-Co3(Nb,V), measured as Co3(Nb0.81V0.19) by APT, respectively. This shows that these ternary γ′ phases are metastable and points to the need for their stabilization via additional alloying elements.
KW - Atom probe tomography (APT)
KW - Cobalt-base superalloys
KW - Intermetallic phases
KW - Microstructure
KW - Precipitates
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U2 - 10.1016/j.actamat.2018.03.057
DO - 10.1016/j.actamat.2018.03.057
M3 - Article
AN - SCOPUS:85045050363
SN - 1359-6454
VL - 151
SP - 137
EP - 148
JO - Acta Materialia
JF - Acta Materialia
ER -