形狀記憶合金性能增進之研究─子計畫三--增進鐵基形狀記憶合金記憶性能之研究(3/3)
Date Issued
2005
Date
2005
Author(s)
DOI
932216E002025
Abstract
The purpose of this three-year research is to investigate the relation between the deformation
texture of FeMnSiCr shape memory alloy and the shape memory effect when the FeMnSiCr
shape memory alloy is under various conditions of plastic deformation and annealing, and to
show the difference of thermo-mechanical behavior of the FeMnSiCr shape memory alloy in
various recovery temperature and tensile strain. In addition, the relation between the dislocations
or stacking faults of the alloys and the relaxation effect is studied when the FeMnSiCr shape
memory alloys are under various conditions of compressive stress relaxation tests. The difference
of the stress relaxation of the alloys at various thermal cycling and constant temperatures is also
examined.Experimental results showed that the major fiber of the FeMnSiCr alloy by different
thermo-mechanical treatment is the ζ fiber which parallels to the normal direction. With various
strain and deformation temperature, several directions of the deformation texture or reorientation
texture can be formed. Stacking faults can be formed by thermo-mechanical training. Thus, the
stacking fault probability increases, and the critical shear stress for inducing martensite is reduced.
At higher recovery temperatures, the cyclic hardening effect can be reduced by eliminating the
density of the dislocations, and the stress-induced martensite can recover to the parent phase γ
completely. The relaxation phenomenon of the FeMnSiCr alloy becomes negligible after about
six hours at room temperature. The thermal stress and shape recovery effect of the FeMnSiCr
shape memory alloys cause the stress relaxation under the stress and thermal cycling. The
relaxation is quite obvious when the hysteresis of the cycling raises, and it tends to the
equilibrium state of stresses after several thermal cycling. The relaxation effect of the alloys is
attributed to the transformation of the higher strain energy region into the lower one by the
rearrangement of dislocations and stacking faults to reduce the internal strain energy. The
stacking faults of the secondary orientation are also induced with increasing the numbers of
thermal cycling in addition to the primary orientation arrays. The extent of the change is
proportional to the cyclic temperature, and the unstable structure of the alloys directly affects the relaxation which increases with increasing the numbers of thermal cycling.
Subjects
Fe-based shape memory alloy
Deformation texture
Thermo-mechanical training
Compressive stress relaxation
Thermal cycling
Publisher
臺北市：國立臺灣大學材料科學與工程學系暨研究所
Type
report
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