Molecular dynamics simulation of the martensitic phase transformation in NiAl alloys

Abstract

Using molecular dynamics simulations with an embedded-atom interatomic potential, we study the effect of chemical composition and uniaxial mechanical stresses on the martensitic phase transformation in Ni-rich NiAl alloys. The martensitic phase has a tetragonal crystal structure and can contain multiple twins arranged in domains and plates. The transformation is reversible and is characterized by a significant temperature hysteresis. The magnitude of the hysteresis depends on the chemical composition and stress. We show that applied compressive and tensile stresses reduce and can even eliminate the hysteresis. Crystalline defects such as free surfaces, dislocations and anti-phase boundaries reduce the martensitic transformation temperature and affect the microstructure of the martensite. Their effect can be explained by heterogeneous nucleation of the new phase in defected regions.

Development and application of a Ni-Ti interatomic potential with high predictive accuracy of the martensitic phase transition

“…We attribute the large theoretical hysteresis to (1) the absence of heterogeneous nucleation sites such as defects and (2) the prevention of active habit planes as the size of the simulation cell is tiny compared to that of experimental samples. The importance of heterogeneous nucleation sites was reported in previous MD simulations on the phase transition of a NiAl shapememory alloy [84][85][86][87][88]. These works also resulted in a large thermal hysteresis (≈1000 K) if simulations were started using defect-free crystals, in accordance with our present finding.…”

“…These works also resulted in a large thermal hysteresis (≈1000 K) if simulations were started using defect-free crystals, in accordance with our present finding. Further simulations considering various kinds of defects, such as a dislocation [85], a grain boundary [84,88], an antiphase boundary [85], and a free surface [85,86], confirmed that such defects can significantly reduce the thermal hysteresis window. Figure 11(a) also illustrates the occurrence of a solid-liquid phase transition upon continued heating of the solid phase to higher temperatures.…”

Interatomic potential for the ternary Ni–Al–Co system and application to atomistic modeling of the B2–L10martensitic transformation

“…To demonstrate the ability of the new Ni-Al-Co potential to reproduce the martensitic phase transformation, a series of atomistic simulations was conducted for various chemical compositions. In the previous study of the binary Ni-Al system [15], the austenitic phase was first equilibrated at temperature of 1200 K by semi-grand canonical Monte Carlo simulations to create an equilibrium state of long-and short-range order. The austenite was then subject to cooling and heating cycles by molecular dynamics (MD) simulations to observe the martensitic transformation.…”

“…The martensitic phase was found to contain multiple twins arranged in domains and plates, with crystallographic characteristics consistent with experimental observations. This study [15] utilized an embedded-atom method (EAM) potential [16] that had been constructed by adopting previously developed Ni [17] and Al [18] potentials and fitting the cross-interaction function to a database of first-principles and experimental data. The ability of this potential to correctly reproduce the thermodynamics and crystallography of the martensitic phase transformation in the binary Ni-Al system was demonstrated in [15].…”

“…This study [15] utilized an embedded-atom method (EAM) potential [16] that had been constructed by adopting previously developed Ni [17] and Al [18] potentials and fitting the cross-interaction function to a database of first-principles and experimental data. The ability of this potential to correctly reproduce the thermodynamics and crystallography of the martensitic phase transformation in the binary Ni-Al system was demonstrated in [15]. An additional advantage of the potential [19] for the modeling of sensory particles embedded in Al matrix is that the constituent Al potential [18] has been extensively tested and is widely used for the modeling of deformation and fracture of this material.…”