Alloy composition, deformation temperature, pressure and post-deformation annealing effects in severely deformed Ti–Ni based shape memory alloys

The α → ω Transformation in Titanium-Cobalt Alloys under High-Pressure Torsion

“…SPD also induces various phase transformations [12] such as formation [13][14][15] or decomposition [16][17][18][19][20] of supersaturated solid solution, dissolution of particles of a second solid phase [21][22][23][24][25][26], amorphization [27][28][29][30][31][32] and nanocrystallization [33][34][35]. Among this variety, very interesting are the phase transformations with formation of high-pressure phases.…”

Anomalous Temperature Dependence of Crystalline-to-Amorphous Transformation Induced by High-Pressure Torsion in Zr₅₀(Cu,Al)₅₀

“…These results suggest that increasing T def toward A s (well above M s ) in both compounds can enhance the formation of amorphous phase, which is in contradiction to the previous observations that the tendency to form amorphous structure in NiTi deformed by HPT is most pronounced when T def is below M s . 13) The possible explanation for this difference may be related to the different rotation speed, which is 1 rpm in present study and 11.6 rpm in the reference. 13) In the present study, the accumulative shear strain imposed by HPT is identical for the all conditions, but the fraction of amorphous structure is significantly different, indicating the amorphization in both alloys is strongly dependent on the T def .…”

“…13) The possible explanation for this difference may be related to the different rotation speed, which is 1 rpm in present study and 11.6 rpm in the reference. 13) In the present study, the accumulative shear strain imposed by HPT is identical for the all conditions, but the fraction of amorphous structure is significantly different, indicating the amorphization in both alloys is strongly dependent on the T def . Possible understanding of the present results can be made by considering the generalized Lindemann melting criterion 4) and lattice instability near reverse martensitic transition temperature.…”

“…13,14) The tendency to form amorphous structure by HPT in TiNi is reported to be the most pronounced when the T def is far below the martensitic transformation starting temperature (M s ), intermediate when the T def lies somewhat above M s , and the weakest when T def is far above M s . 13) However, it is still unknown if this tendency may be applied to other materials with higher M s , such as Zr 50 Cu 50 , which undergoes martensitic transformation from B2 to Cm or B19' phases at 443 K. 15) Previous study revealed that M s in ZrCu decreases by an Al addition 16) and Zr(Cu,Al) are also favorable for producing amorphous structure by either rapid quenching or CTAT, 7,17) which is suitable for the investigation of temperature dependence of amorphization. In the present study, the effect of T def on the amorphization process under HPT deformation was investigated in Zr 50 Cu 50 and Zr 50 Cu 44 Al 6 .…”

Application of nanostructural nickel titanium implants with shape memory effect to modern dental practice

“…These boundaries can play the role of Due to record functional properties and mechanical reliability, high stability of the properties, durability, corrosion resistance, and biocompatibility the nanostructured NiTi alloys produced by ECAP are recognized like new generation of TiNi alloys with unique properties for medical application. More information about functional properties of nanostructured TiNi alloy is given in the works [3,4].…”