Multiaxial stress–strain response and displacive transformations in NiTi alloy from first principles

First-Principles Calculations of Structural, Mechanical, and Electronic Properties of the B2-Phase NiTi Shape-Memory Alloy Under High Pressure

“…Moreover, a 0 and V 0 indicated the equilibrium lattice constant and primitive cell volume under the ground state, respectively. The calculated results fit well with the other theoretical [14][15][16]19,[34][35][36][37][38] and experimental results [34,39], and these are compared in Table 2.…”

“…As the representative shape-memory alloys (SMAs), NiTi alloys have been extensively applied in medicine, aerospace, automotive, electronics, machinery, and other industries [1][2][3][4][5][6][7][8], which ascribes to their excellent properties of shape memory effects (SMEs), superelasticity (SE), high-strength, corrosion resistance, and biocompatibility [9][10][11][12][13]. For the studies of NiTi SMAs, plenty of works have been carried out by theory and experiment [14][15][16][17][18]. Haskins and Lawson [19] investigated the temperature-dependent thermodynamic properties of NiTi alloys by density functional theory molecular dynamics (DFT-MD), and then analyzed the finite temperature properties of three phases (ground state monoclinic B33, martensitic B19', and austenitic B2), and the results revealed that the anharmonic effects played a large role in both stabilizing the austenite B2 phase and suppressing the martensitic phase transition.…”

Ab initio prediction of phase stability of martensitic structures in binary NiTi under hydrostatic tension

“…Wagner and Windl [12] revealed that increasing a resistive shear to the monoclinic inclination of BCO can reduce its monoclinic angle and eventually destabilise it relative to B19′. Sestak et al [19] used the same method and confirmed Wagner and Windl's findings. In these analyses B19″ was absent (not mentioned).…”

“…Table 1 also reveals the unit cell volume (V ), lattice constants (a, b, and c), monoclinic angle γ (°), and energy difference relative to B2 (E − E B2 ) of those studied phases. The calculations revealed that both phases are energetically more favourable than B19′ and that the BCO phase is the ground state at 0 K [7,[11][12][13][14][15][16][17][18][19][20][21]. In addition, the experimentally observed B19′ phase is not an energetically stable phase in ab initio calculations [7,10,16,22].…”

“…One is the resistive shear stress self-generated by the monoclinic lattice distortions of the two phases, forcing the system to take a form of lower monoclinic lattice distortion, i.e. the B19′ phase [12,19]. The other is that the B2→B19″ and B2→BCO transformations are associated with volume expansions and the self-generated hydrostatic pressure forces the system to take a form of lower volume expansion, i.e.…”