Prediction of precipitate evolution and martensite transformation in Ti-Ni-Cu shape memory alloys by computational thermodynamics

Thermodynamic and Kinetic Simulations Used for the Study of the Influence of Precipitates on Thermophysical Properties in NiTiCu Alloys Obtained by Spark Plasma Sintering

“…Our multi-component SMA database includes the low-temperature martensitic phases B19 and B19′. These phases have been described in the pure Ni-Ti system by Tang [ 41 ]; however, their description required some re-parametrization in order to allow for combination with the Ni-Ti assessment by Povoden-Karadeniz et al [ 38 ] and the extension to Ni-Ti-Cu, which has been discussed in [ 17 ]. After rejecting the austenitic B2 phase and intermetallic phases from the computation, we may interpret the relative metastability of orthorhombic B19 versus monoclinic B19′ and their changes with increasing Cu alloying and balanced (Ni, Cu):Ti, as seen in Figure 4 b.…”

“…In order to relate the thermal evolution of the studied alloys with thermophysical properties, Calphad-evaluated phase stabilities in the ternary system Ni-Ti-Cu [ 17 ] are compared with XRD analyses of the samples. Thermokinetic aging simulations at 850 °C and 500 °C are performed with the solid-state transformation software MatCalc [ 30 ].…”

“…Optimizing the sintering and heat treatment conditions for ternary SMAs has recently been supported by Calphad computational thermodynamics and Calphad-based kinetic simulation [ 17 ]. Povoden-Karadeniz et al [ 17 ] established a thermodynamic Ti-Ni-Cu SMA database, containing the stable and metastable phases of this system.…”

“…Optimizing the sintering and heat treatment conditions for ternary SMAs has recently been supported by Calphad computational thermodynamics and Calphad-based kinetic simulation [ 17 ]. Povoden-Karadeniz et al [ 17 ] established a thermodynamic Ti-Ni-Cu SMA database, containing the stable and metastable phases of this system. In a computational thermokinetic evaluation of temperature- and aging time-dependent precipitation in Cu-alloyed Ti-Ni SMA, the assessed thermodynamics are combined with kinetic models for diffusion, nucleation and growth of precipitates, as implemented in the solid-state transformation of MatCalc software, version 6.03 [ 18 ].…”

“…Taking into account the above-mentioned, the aim of this work is to continue the investigations started in [ 6 , 17 ] and the understanding of the processing—microstructure correlation including precipitation—and MT—thermophysical properties of NiTiCu materials through supportive computational thermodynamics. Also, the current work compiles a thermodynamic model to simulate the sintering and aging evolution of NiTiCu materials obtained by SPS with and without MA.…”