Process-performance tuning of a NiTiPt alloy for medical and elastocaloric applications

Dr. Dick James and team have shown that the NiTiPt ternary system is capable of approaching λ₂ = 1 with concomitant reduction of thermal and stress hysteresis due to the approach of an exact austenite-martensite interface [1]. The material composition for minimal thermal hysteresis is approximately Ti₅₀Ni_42.5Pt_7.5 where several authors have corroborated this outcome, but no material has achieved commercial significance. Improved crystallographic compatibility may improve structural and functional fatigue of the system in respectively medical and elastocaloric systems. Further, as mentioned elsewhere since the 1990s, such alloys can raise x-ray visibility in neurovascular device placement procedures. Here, three alloys are prepared by arc melt casting, namely Ti_49.8Ni_42.7Pt_7.5, Ti_49.8Ni_40.2Pt₁₀, and Ti_49.6Ni_40.4Pt₁₀. After initial processing and evaluation, two are set aside, and the first is evaluated over a wide cold work and heat treatment spectrum in a 25 to 100 µm wire format for process-performance tuning impact. Finally, results are presented toward optimization of cyclic uniaxial tension properties, functional fatigue, and structural fatigue of a high compatibility, low hysteresis, and radiopaque NiTiPt wire.

[1] Zhang, Zhiyong, Richard D. James, and Stefan Müller. "Energy barriers and hysteresis in martensitic phase transformations." Acta Materialia 57.15 (2009): 4332-4352.