D. Treppmann et al., THE EFFECT OF COMBINED RECRYSTALLIZATION AND PRECIPITATION PROCESSES ON THE FUNCTIONAL AND STRUCTURAL-PROPERTIES IN NITI ALLOYS, Journal de physique. IV, 5(C8), 1995, pp. 569-574
To obtain an optimum shape memory component, functional and structural
properties have to be connected during fabrication. To fulfil these r
equirements thermomechanical treatments are used to generate favourabl
e microstructures by ''combined reactions''. Combined reactions can be
composed of recrystallization, precipitation and phase transformation
. All of these solid-state reactions are able to influence each other
and subsequently the reversible phase transformations. To distinguish
between the effects of exclusive precipitation, exclusive recrystalliz
ation and combined reactions, two different compositions of NiTi-alloy
s were chosen (with low tendency for precipitation 50.2 at% Ni and wit
h higher tendency 50.8 at% Ni). The alloys have been modified systemat
ically by aging, plastic deformation and combinations of both. For cha
racterization light microscopy (LM) and transmission electron microsco
py (TEM) are combined with hardness tests and DSC-measurements. The re
sults of investigation are plotted in time-temperature-reaction diagra
ms (t-T-r).