Effect of yttrium on martensite-austenite phase transformation temperatures and high temperature oxidation kinetics of Ti-Ni-Hf high-temperature shape memory alloys

Recent Development of TiNi‐Based Shape Memory Alloys with High Cycle Stability and High Transformation Temperature

“…The solubility of Y in Ti 36 Ni 49 Hf 15 alloy is limited to 0.2 at%, resulting in the formation of a Y-rich phase distributed along the grain boundary. [89,90] According to the energy-dispersive X-ray spectroscopy results, the Y-rich phase was suggested to be (Ti,Hf, Y) 2 Ni with Y content ranging from 28 to 32 at%. [89,90] When Ag was added to Ti 36 Ni 49 Hf 15 alloy, pure Ag particles were present, in addition to the (Ti,Hf ) 2 Ni phase.…”

“…[89,90] According to the energy-dispersive X-ray spectroscopy results, the Y-rich phase was suggested to be (Ti,Hf, Y) 2 Ni with Y content ranging from 28 to 32 at%. [89,90] When Ag was added to Ti 36 Ni 49 Hf 15 alloy, pure Ag particles were present, in addition to the (Ti,Hf ) 2 Ni phase. [79] The alloying of Sn in Ti 36 Ni 49 Hf 15 alloy results in the formation of Ti 3 Sn and TiNi 2 Sn phases.…”

“…Figure 9 shows the effect of alloying elements on the M s of TiNiHf-based alloys. [79,[87][88][89][90]98,101,103,104,[112][113][114][115][116][117][118] alloys, [112] which is the largest value among the reported results. In contrast, the alloying of Y has an insignificant effect on the TT (%1-1.5 C at% À1 ).…”

“…In contrast, the alloying of Y has an insignificant effect on the TT (%1-1.5 C at% À1 ). [89,90] The alloying of Zr plays a different role, which elevates the TT. For example, the A s of Ti 38Àx Ni 50 Hf 12 Zr x alloys increases from 110 to 560 C with the Zr content increasing from 0 to 15 at%.…”

“…Alloying of Ni‐lean TiNiHf alloys leads to the formation of additional phases in the matrix. Several quaternary elements have been added to Ti 36 Ni 49 Hf 15 alloy, including Nb, Ta, Y, Ag, Sn, and Sc . The alloying of Nb and Ta reduces the amount of the (Ti,Hf) 2 Ni phase and forms Nb‐rich and Ta‐rich phases, respectively, because of their limited solubility in the TiNiHf matrix .…”