TY - JOUR
T1 - Influence of heat treatment on microstructure and mechanical properties of Nb-Ti-Si-Cr-Ta ultrahigh temperature alloys
AU - Li, Anni
AU - Guo, Xiping
N1 - Publisher Copyright:
© 2026 Elsevier Ltd.
PY - 2026/11
Y1 - 2026/11
N2 - A series of multi-component Nb-22Ti-14.8Si-4Cr-xTa (x = 0, 2, 4, 8 at.%) alloys were prepared via vacuum non-consumable arc melting and subsequent two-step homogenization heat treatment (1300 °C/20 h + 1450 °C/50 h). The microstructural evolution upon heat treatment was analyzed, and the influences of Ta content on the microstructure and mechanical properties of the heat-treated alloys were systematically investigated. The as-cast alloys possess a hypereutectic microstructure, consisting of primary (Nb,X)5Si3 blocks, Nbss/γ(Nb,X)5Si3 eutectics, and Nbss/γ(Nb,X)5Si3/Cr2(Nb,X) three-phase eutectics. After heat treatment, the three-phase eutectics have been completely eliminated, and a small amount of (Nb,X)3Si is newly precipitated. Ta addition promotes the formation of α(Nb,X)5Si3 phase by enhancing its thermodynamic stability. Ta exhibits a significantly higher partitioning preference in α(Nb,X)5Si3 phase than in γ(Nb,X)5Si3 phase. Heat treatment effectively optimizes the microstructural homogeneity of the alloys, thus significantly enhancing their room temperature fracture toughness and high temperature compressive strength. Higher Ta contents (4 and 8 at.%) addition further elevates the high temperature (1250 °C) compressive strength of the heat-treated alloys, reaching a maximum value of approximately 616 MPa. Ta addition improves the nanoindentation hardness of both Nbss and primary α(Nb,X)5Si3 blocks through solid solution strengthening, and heat treatment further enhances the nanoindentation hardness of silicides.
AB - A series of multi-component Nb-22Ti-14.8Si-4Cr-xTa (x = 0, 2, 4, 8 at.%) alloys were prepared via vacuum non-consumable arc melting and subsequent two-step homogenization heat treatment (1300 °C/20 h + 1450 °C/50 h). The microstructural evolution upon heat treatment was analyzed, and the influences of Ta content on the microstructure and mechanical properties of the heat-treated alloys were systematically investigated. The as-cast alloys possess a hypereutectic microstructure, consisting of primary (Nb,X)5Si3 blocks, Nbss/γ(Nb,X)5Si3 eutectics, and Nbss/γ(Nb,X)5Si3/Cr2(Nb,X) three-phase eutectics. After heat treatment, the three-phase eutectics have been completely eliminated, and a small amount of (Nb,X)3Si is newly precipitated. Ta addition promotes the formation of α(Nb,X)5Si3 phase by enhancing its thermodynamic stability. Ta exhibits a significantly higher partitioning preference in α(Nb,X)5Si3 phase than in γ(Nb,X)5Si3 phase. Heat treatment effectively optimizes the microstructural homogeneity of the alloys, thus significantly enhancing their room temperature fracture toughness and high temperature compressive strength. Higher Ta contents (4 and 8 at.%) addition further elevates the high temperature (1250 °C) compressive strength of the heat-treated alloys, reaching a maximum value of approximately 616 MPa. Ta addition improves the nanoindentation hardness of both Nbss and primary α(Nb,X)5Si3 blocks through solid solution strengthening, and heat treatment further enhances the nanoindentation hardness of silicides.
KW - Homogenization heat treatment
KW - Mechanical properties optimization
KW - Microstructural evolution
KW - Nb-Si based ultrahigh temperature alloys
KW - Ta alloying
UR - https://www.scopus.com/pages/publications/105047924454
U2 - 10.1016/j.intermet.2026.109510
DO - 10.1016/j.intermet.2026.109510
M3 - 文章
AN - SCOPUS:105047924454
SN - 0966-9795
VL - 198
JO - Intermetallics
JF - Intermetallics
M1 - 109510
ER -