Influence of the Nb Content on the Microstructure and Phase Transformation Properties of NiTiNb Shape Memory Alloys

Abstract

NiTi shape memory alloys (SMAs), as smart materials, are broadly used in medical implants and appliances despite the presence of toxic Ni. In this study, NiTiNb alloys were produced using the substitution of biocompatible Nb instead of Ni. The arc-melting method was utilized to make five SMA samples comprising Ni (29Àx) Ti 50 Nb (21+x ) (x = 0, 1, 2, 3, and 4); then, the phase transformation temperatures, microstructures, crystal structures, and chemical compositions were investigated by DSC, optical microscopy, XRD, and EDX measurements, respectively. The DSC results showed that the samples had a wide hysteresis with the B19¢MB2 phase transformation and martensite start temperatures below room temperature, which makes them suitable for superelastic implants. The presence of dissolved Nb in the matrix of the alloys was the main reason for the widening of temperature hysteresis. When the XRD and SEM results were examined, the b-rich, B2, B19¢, and Ti 2 Ni phases were observed in all samples. Additionally, the main constituent in the dendritic microstructures was Nb.

Quaternary Element Incorporation Effects on Thermal Properties and Crystal-Micro Structure of Cu-Al-Fe High Temperature Shape Memory Alloys

“…Entropy is another physical parameter that can change throughout a thermodynamic process. The entropy change in an austenite transformation process (∆ → ) can be calculated by the following formula [3,[29][30][31]:…”

Recent Improvements in Renewable Energies and their effects on the Environment and the Economy: Review Article

“…There are also many engineer types such as piezoelectric materials [37] that are used in a robotic and ultrasound generator, moreover, they are used for power generating sidewalks [38]. Another type is shape memory alloys (SMAs) that their properties have been improved for Cu-based SMAs [39][40][41][42][43][44][45], NiTi-based SMAs [46][47][48][49][50][51][52][53][54], and Fe-based SMAs [55][56][57]. The aforementioned materials can be used for smart systems that generate clean energies.…”

The Effect of Different Parameters on Shape Memory Alloys

“…The phase transformation temperatures are austenite start, austenite finish, martensite start, martensite finish and martensite transformation temperature by deformation (i.e. maximum temperature at which martensite transformation occurs) Temperatures that are symbolized as As, Af, Ms, Mf, and Md, respectively [17][18][19][20][21][22][23][24][25][26][27][28][29].…”