Sitepu, H.; Klonne, M.; Schmahl, Wolfgang W.; Predki, W.; Pirling, T.
Measurements of strain, texture and phase fraction in aged Ni-rich NiTi shape memory alloys by neutron powder diffraction technique under in situ torsional loading.
In: Journal de Physique IV, Vol. 112, No. 2: pp. 811-814
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hollow shaft of superelastic Ti-50.8 atomic percent nickel shape memoryalloy has been investigated under torsional load by neutron diffraction.To optimize superelasticity the material was solution-annealed at850degreesC for 15 minutes, water quenched, and subsequently aged at500degreesC for 15 minutes. The torsional load was applied instrain-controlled mode and both torque and torsion angle were measured.The neutron diffraction data were analyzed by the Rietveld refinementprogram GSAS with a generalized spherical harmonic model for preferredorientation (or texture) to determine phase fractions andcrystallographic properties for B2 and B19’ during the forward andreverse transformation which are associated with the acquired mechanicalhysteresis curve.