In the work to be presented, vacuum plasma spray forming has been used as a process to deposit and consolidate prealloyed
NiTi and NiTiPd powders into near net shape actuators. Testing showed that excellent shape memory behavior
could be developed in the deposited materials and the investigation proved that VPS forming could be a means to
directly form a wide range of shape memory alloy components. The results of DSC characterization and actual actuation
test results will be presented demonstrating the behavior of a Nitinol 55 alloy and a higher transition temperature NiTiPd
alloy in the form of torque tube actuators that could be used in aircraft and aerospace controls.
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 Mf and superelasticity (SE) above Af. 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.