TY - JOUR
T1 - Effects of Cr and Hf additions on the microstructure and properties of Nb silicide based ultrahigh temperature alloys
AU - Zhang, Song
AU - Guo, Xiping
N1 - Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/6/5
Y1 - 2015/6/5
N2 - Four Nb silicide based ultrahigh temperature alloys with compositions of Nb-22Ti-16Si-3Al-2B-xHf-yCr ((x, y)=(0, 0), (0, 5), (4, 0) and (4, 5)) (at%) were prepared by vacuum non-consumable arc melting. The effects of Cr and Hf additions on the phase selection, microstructure, room-temperature fracture toughness and oxidation resistance at 1250°C of the alloys have been investigated. The results show that all the four alloys are comprised of primary silicides and Nbss dendrites together with one or two types of eutectic. The Cr addition does not change the crystal structures of 5-3 silicides but imposes a significant influence on the amount, size and morphology of the constituent phases. The Hf addition suppresses the formation of α(Nb,X)5Si3 but promotes the formation of γ(Nb,X)5Si3. The combined additions of Cr and Hf also cause the formation of Cr2(Nb,X) containing three-phase eutectic. The room-temperature fracture toughness of the alloys decreases with Cr addition while increases with Hf addition. The oxidation-resistant performance of the alloys has been ameliorated by Cr addition, while it has been significantly degraded by Hf addition in the absence of Cr. Furthermore, the formation mechanism of the scale has been illustrated.
AB - Four Nb silicide based ultrahigh temperature alloys with compositions of Nb-22Ti-16Si-3Al-2B-xHf-yCr ((x, y)=(0, 0), (0, 5), (4, 0) and (4, 5)) (at%) were prepared by vacuum non-consumable arc melting. The effects of Cr and Hf additions on the phase selection, microstructure, room-temperature fracture toughness and oxidation resistance at 1250°C of the alloys have been investigated. The results show that all the four alloys are comprised of primary silicides and Nbss dendrites together with one or two types of eutectic. The Cr addition does not change the crystal structures of 5-3 silicides but imposes a significant influence on the amount, size and morphology of the constituent phases. The Hf addition suppresses the formation of α(Nb,X)5Si3 but promotes the formation of γ(Nb,X)5Si3. The combined additions of Cr and Hf also cause the formation of Cr2(Nb,X) containing three-phase eutectic. The room-temperature fracture toughness of the alloys decreases with Cr addition while increases with Hf addition. The oxidation-resistant performance of the alloys has been ameliorated by Cr addition, while it has been significantly degraded by Hf addition in the absence of Cr. Furthermore, the formation mechanism of the scale has been illustrated.
KW - Alloying
KW - Microstructure
KW - Nb silicide based ultrahigh temperature alloy
KW - Oxidation resistance
KW - Room-temperature fracture toughness
UR - http://www.scopus.com/inward/record.url?scp=84929070343&partnerID=8YFLogxK
U2 - 10.1016/j.msea.2015.04.003
DO - 10.1016/j.msea.2015.04.003
M3 - 文章
AN - SCOPUS:84929070343
SN - 0921-5093
VL - 638
SP - 121
EP - 131
JO - Materials Science and Engineering: A
JF - Materials Science and Engineering: A
ER -