Effect of texture orientation on the martensite deformation of NiTi shape memory alloy sheet
- Catholic Univ. of Leuven, Heverlee (Belgium)
For a cold-rolled NiTi sheet, the tensile stress-strain curves show a flat stress-plateau during tension along the rolling direction, while under tension along the transverse direction the specimens are quickly strain-hardened and no flat stress-plateau occurred. This shows that the deformation mechanisms of martensite twins are different when loading along different directions. TEM observations show that, in the as-annealed condition, the major type of twins in the martensite phase is {l_angle}011{r_angle} type II twins in the present material. Also present are (001) compound twins and a small amount of (111) type I twins. Deformation details of these three types of twins are different along rolling and transverse directions. After deformation along the rolling direction to 6% strain, reorientation and de-twinning of the {l_angle}011{r_angle} type II twins have been observed. Instead, a high density of dislocations has been generated inside the {l_angle}011{r_angle} type II twins and de-twinning of the (001) compound twins has been observed. A further crystallographic analysis shows that the shear direction of each type of martensite twins relative to the loading direction is different, which may explain the different deformation behavior of the twins. This may also account for the macroscopical deformation behavior of the material.
- OSTI ID:
- 329062
- Journal Information:
- Acta Materialia, Vol. 47, Issue 2; Other Information: PBD: 15 Jan 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Evolution of Intergranular Stresses in a Martensitic and an Austenitic NiTi Wire During Loading–Unloading Tensile Deformation
Tension-compression asymmetry of the stress-strain response in aged single crystal and polycrystalline NiTi