TiNi shape memory alloy has been used in many application fields due to its excellent shape memory effect (SME) and superelasticity (SE). However, it is difficult and costly to machine TiNi alloy into complex shapes due to its low ductility. To address this problem, one approach is near-net shape processing by vacuum plasma spraying (VPS). In this study, the transformation behavior, mechanical properties and microstructure of TiNi alloy processed by VPS method are studied. The as-sprayed and homogenized TiNi alloy exhibited compositional variations in the sample, though both samples exhibited a single TiNi phase with low transformation temperatures, below 170 K Aging the homogenized sample at 773 K for 18 ks led to an increase in the transformation temperature, resulting in good transformation behavior. Specifically, DSC measurement revealed clear transformation peaks due to Martensite, austenite and R-phase transitions. Compression testing of a sample aged at 773 K for 18 ks exhibited a good SME below M_f and superelasticity (SE) above A_f. The recoverable strain due to SME and SE were more than 2.4 % and 5.0 %, respectively. TEM studies confirmed that aTi₃Ni₄ precipitate was formed by aging at 773 K for 18 ks.

Date Published: 6 April 2006
PDF: 9 pages
Proc. SPIE 6170, Smart Structures and Materials 2006: Active Materials: Behavior and Mechanics, 61702A (6 April 2006); doi: 10.1117/12.658573

Published in SPIE Proceedings Vol. 6170:
Smart Structures and Materials 2006: Active Materials: Behavior and Mechanics
William D. Armstrong, Editor(s)