Phase transformation temperatures for NiTi alloys prepared by powder metallurgical processes

The phase transformation temperatures (PTTs) of NiTi samples prepared by hot isostatic pressing (HIP) and metal injection moulding (MIM) from two prealloyed powders with a different Ni content were determined and compared to the PTTs of the starting powders and samples sintered from loose powders. T...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2004-07, Vol.378 (1), p.165-169
Main Authors: Schüller, E., Bram, M., Buchkremer, H.P., Stöver, D.
Format: Article
Language:English
Subjects:
Applied sciences
Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Materials science
Materials synthesis
materials processing
Metal powders
Metals. Metallurgy
NiTi
Oxygen
Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
Phase transformation temperature
Physics
Powder metallurgy
Powder metallurgy. Composite materials
Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
Production techniques
PTT
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Summary:The phase transformation temperatures (PTTs) of NiTi samples prepared by hot isostatic pressing (HIP) and metal injection moulding (MIM) from two prealloyed powders with a different Ni content were determined and compared to the PTTs of the starting powders and samples sintered from loose powders. The impurity content of the samples is influenced by the processing. Deviations of up to 50 K were found between the measured PTTs and values given in literature for samples with the same nominal Ni content. To explain these differences, preferentially the formation of Ti-consuming oxides was assumed to change the Ni content of the transforming matrix. Based on the oxygen content of the samples determined by chemical analysis, the Ni content was recalculated and the measured PTTs were correlated to the nominal and the calculated Ni content. It has been shown that the oxygen content itself is not sufficient to explain the influence of the manufacturing route on the PTTs of powder metallurgical (PM) NiTi samples.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2003.10.341