Bimodal size distribution of Ti3Ni4 particles and martensitic transformations in slowly cooled nickel-rich TiNi alloys

Microstructures evolution and phase transformation behaviors of Ni-rich TiNi shape memory alloys after equal channel angular extrusion

“…Because the crystal lattices are similar; the growths of Ti 3 Ni 4 in the B2 matrix favor a B2 → R transformation. By contrast, the B2 → B19 transformation is hampered, because these dispersed particles presented in the matrix would require more additional energy expenditure owing to a higher elastic energy of the system [41]. On the heating curves of DSC for all ECAE samples from the first to the eighth pass, only one endothermic peak was observed, which revealed that the reverse R phase transformation and the reverse martensite phase transformation overlapped together [42].…”

Martensitic Transformations in TiNi Alloys with Ti3Ni4 Precipitates

“…resulting in increase of the B2+B19' transformation temperature. After cooling of the Ti&JiSZ alloy with cooling rate of 1.5-3 "Clmin [5] and the Tid9Ni51 -with 1.0 or 0.6 OCImin rates, the particle sizes are as large as several micrometers (up to 10pm) [6]. The transformation sequence in these cases is B2+B19' (fig.…”

On the effect of room temperature ageing of Ni-rich Ni–Ti alloys

“…Ageing temperatures around 470-570 K are considered as low [1][2][3][4][5][6][7][8][9][10][11][12][13]: this temperature range is well below the recrystallization temperature close to 870 K, and it is believed that no microstructural changes like precipitation occur below approximately 470 K. For instance, Kim and Miyazaki did not observe by transmission electron microscopy any traces of precipitation after ageing for 3.8 ks at 370 K of a Ni 50.9 Ti 49.1 alloy quenched from 1070 K [1]. As for the origin of the effect of lowtemperature ageing it is generally agreed that it stems from the formation of precipitates and related variation of the Ni content of the matrix.…”