In situ observation on temperature dependence of martensitic transformation and plastic deformation in superelastic NiTi shape memory alloy

A digital image correlation study of a NiTi alloy subjected to monotonic uniaxial and cyclic loading-unloading in tension

“…In the annealed material in the present work, the predominantly 〈111〉 grains of the B2 phase (inset in Fig. 8a) are suitably oriented for transformation to the B19′ phase during tension [4,12,30].…”

“…Since then, researchers have routinely applied DIC to characterise strain fields during the mechanical testing of thermo-mechanically processed NiTi alloys [3,[9][10][11][12][13][14]. For example, DIC investigations revealed the development of a region of strain concentration upon deviation from linearity towards the end of the elastic region; suggesting the initiation of phase transformation just prior to the onset of the macroscopic stress plateau [1].…”

“…For example, DIC investigations revealed the development of a region of strain concentration upon deviation from linearity towards the end of the elastic region; suggesting the initiation of phase transformation just prior to the onset of the macroscopic stress plateau [1]. Thereafter, further localisation in the strain fields results in Lüders/transformation band(s) that propagate along the gauge length with higher macroscopic tensile strains [1,3,11,12,[14][15][16]. The bands are typically inclined at ~60° with respect to the loading direction [12,[17][18][19][20][21] and divide the gauge length into domains with varying local axial strain extrema comprising fully martensitic and as-yet untransformed B2 regions [11,12,14,15].…”

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

“…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.…”

An in-situ synchrotron study of the B2→B19′ phase transformation in a Ni-Ti alloy subjected to uniaxial monotonic tension

“…In-situ digital image correlation (DIC) studies of NiTi alloys subjected to uniaxial monotonic tension have revealed that upon yielding, the localised development of strain concentration occurs at one end of the parallel gauge length; marking the initiation of phase transformation prior to the onset of the macroscopic stress plateau region [1,9]. Higher macroscopic tensile strains result in further strain field localisation that cause the Lüders/transformation band, typically inclined at ~60° with respect to the axial/loading direction [10][11][12], to propagate along the gauge length [1,2,4,9,10]. Within the macroscopic stress plateau region, the gauge length is sub-divided into three general regions.…”