An In Situ Study of Sintering Behavior and Phase Transformation Kinetics in NiTi Using Neutron Diffraction

Gang Chen, Klaus Dieter Liss, Peng Cao*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

The powder sintering behavior of NiTi from an elemental powder mixture of Ni/Ti has been investigated, using an in situ neutron diffraction technique. In the sintered alloys, the overall porosity ranges from 9.2 to 15.6 pct, while the open-to-overall porosity ratio is between 8.3 and 63.7 pct and largely depends on the sintering temperature. In comparison to powder compacts sintered at 1223 K and 1373 K (950 °C and 1100 °C), the powder compact sintered at 1153 K (880 °C) shows a much smaller pore size, a higher open-to-overall porosity ratio but smaller shrinkage and a lower density. Direct evidence of eutectoid transformation in the binary Ni-Ti system during furnace cooling to ca. 890 K (617 °C) is provided by in situ neutron diffraction. The intensities of the B2-NiTi reflections decrease during the holding stage at 1373 K (1100 °C), which has been elaborated as an extinction effect according to the dynamical theory of neutron diffraction, when distorted crystallites gradually recover to perfect crystals. The analysis on the first five reflections clarifies the non-existence of any order–disorder transition in the NiTi phase from B2-to-BCC structure.

Original languageEnglish
Pages (from-to)5887-5899
Number of pages13
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume46
Issue number12
DOIs
StatePublished - 1 Dec 2015
Externally publishedYes

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