AN INTERPLAY BETWEEN HEAT TREATMENT CONDITIONS AND B2 <-> B19 ' TRANSFORMATION IN Ni-Ti SHAPE MEMORY ALLOYS

Kód výsledku v IS VaVaI

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Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

AN INTERPLAY BETWEEN HEAT TREATMENT CONDITIONS AND B2 <-> B19 ' TRANSFORMATION IN Ni-Ti SHAPE MEMORY ALLOYS

Popis výsledku v původním jazyce

This study investigates the influence of a heat treatment atmosphere on multistage martensitic transformations in a Ti-50.9at% Ni shape memory alloy. Evacuated quartz tubes were filled with hydrogen while the hydrogen partial pressure was carefully controlled in each experiment. The encapsulated specimens were subjected to heat treatments consisting of annealing and aging. After the heat treatment, the path of martensitic transformation was investigated using differential scanning calorimetry (DSC). On cooling, martensite initial temperatures decrease with the increasing partial pressure of hydrogen applied during the heat treatment. Moreover, the formation of martensite phase may not take place for partial pressures that exceed a certain limit. On the other hand, two-and multiple-step B2/R/B19' martensitic transformations are observed in specimens heat treated at lower hydrogen pressures. Results obtained using transmission electron microscopy (TEM) clearly show that the size of Ni4Ti3 precipitates becomes smaller in alloys that were heat treated at higher hydrogen pressures. The results are discussed in terms of a chain of events. It is suggested that diffusion of hydrogen into the specimen during the annealing step first influences the nucleation of the Ni4Ti3 phase. The sizes and distribution of the Ni4Ti3 precipitates than control the characteristics of B2/B19' transformation.

Název v anglickém jazyce

AN INTERPLAY BETWEEN HEAT TREATMENT CONDITIONS AND B2 <-> B19 ' TRANSFORMATION IN Ni-Ti SHAPE MEMORY ALLOYS

Popis výsledku anglicky

This study investigates the influence of a heat treatment atmosphere on multistage martensitic transformations in a Ti-50.9at% Ni shape memory alloy. Evacuated quartz tubes were filled with hydrogen while the hydrogen partial pressure was carefully controlled in each experiment. The encapsulated specimens were subjected to heat treatments consisting of annealing and aging. After the heat treatment, the path of martensitic transformation was investigated using differential scanning calorimetry (DSC). On cooling, martensite initial temperatures decrease with the increasing partial pressure of hydrogen applied during the heat treatment. Moreover, the formation of martensite phase may not take place for partial pressures that exceed a certain limit. On the other hand, two-and multiple-step B2/R/B19' martensitic transformations are observed in specimens heat treated at lower hydrogen pressures. Results obtained using transmission electron microscopy (TEM) clearly show that the size of Ni4Ti3 precipitates becomes smaller in alloys that were heat treated at higher hydrogen pressures. The results are discussed in terms of a chain of events. It is suggested that diffusion of hydrogen into the specimen during the annealing step first influences the nucleation of the Ni4Ti3 phase. The sizes and distribution of the Ni4Ti3 precipitates than control the characteristics of B2/B19' transformation.

Druh

D - Stať ve sborníku

CEP obor

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OECD FORD obor

20501 - Materials engineering

Projekt

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Návaznosti

Z - Vyzkumny zamer (s odkazem do CEZ)

Rok uplatnění

2010

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název statě ve sborníku

METAL 2010: 19TH INTERNATIONAL METALLURGICAL AND MATERIALS CONFERENCE

ISBN

978-80-87294-17-8

ISSN

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e-ISSN

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Počet stran výsledku

6

Strana od-do

877-882

Název nakladatele

TANGER LTD

Místo vydání

Ostrava

Místo konání akce

Rožnov pod Radhoštěm

Datum konání akce

18. 5. 2010

Typ akce podle státní příslušnosti

EUR - Evropská akce

Kód UT WoS článku

000286658700152