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Processing and property assessment of NiTi and NiTiCu shape memory actuator springs
Author(s) -
Grossmann Ch.,
Frenzel J.,
Sampath V.,
Depka T.,
Oppenkowski A.,
Somsen Ch.,
Neuking K.,
Theisen W.,
Eggeler G.
Publication year - 2008
Publication title -
materialwissenschaft und werkstofftechnik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.285
H-Index - 38
eISSN - 1521-4052
pISSN - 0933-5137
DOI - 10.1002/mawe.200800271
Subject(s) - nickel titanium , shape memory alloy , actuator , microstructure , materials science , coil spring , swaging , spring (device) , martensite , metallurgy , mechanical engineering , composite material , structural engineering , engineering , electrical engineering
Among the multifarious engineering applications of NiTi shape memory alloys (SMAs), their use in actuator applications stands out. In actuator applications, where the one‐way effect (1WE) of NiTi SMAs is exploited, SM components are often applied as helical coil springs. Ingots are generally used as starting materials for the production of springs. But before SM actuator springs can be manufactured, the processing of appropriate wires from NiTi ingots poses a challenge because cold and hot working of NiTi SMAs strongly affect microstructure, and it is well known that the functional properties of NiTi SMAs are strongly dependent on their microstructure. The objective of the present paper is therefore to produce binary Ni 50 Ti 50 and ternary Ni 40 Ti 50 Cu 10 SMA actuator springs, starting from ingots produced by vacuum induction melting. From these ingots springs are produced using swaging, rolling, wire drawing and a shape‐constraining procedure in combination with appropriate heat treatments. The evolution of microstructure during processing is characterized and the mechanical properties of the wires prior to spring‐making are documented. The mechanical and functional characteristics of the wires are investigated in the stress‐strain‐temperature space. Finally, functional fatigue testing of actuator springs is briefly described and preliminary results for NiTi and NiTiCu actuator springs are reported.