Title

TRATAMENTO TERMO-CÍCLICO SOB CARGA DA LIGA MONOCRISTALINA Cu-Al-N

UNDER LOAD THERMO-CYCLING TREATMENT OF A MONOCRYSTALLINE Cu- Al-Ni ALLOY

Authorship

Pereira, Elaine Cristina; Matlakhova, Lioudmila Aleksandrovna; Matlakhov, Anatoliy Nikolaevich; Rodríguez, Ruben J. S.; Monteiro, Teresa Ellígio Castilló: Sérgio Neves

Pereira, Elaine Cristina

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Matlakhova, Lioudmila Aleksandrovna

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Matlakhov, Anatoliy Nikolaevich

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Rodríguez, Ruben J. S.

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Monteiro, Teresa Ellígio Castilló: Sérgio Neves

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DOI

10.5151/2594-5327-0335

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Abstract

Neste trabalho foi estudada uma liga monocristalina Cu-13,5%Al-4,0%Ni (em peso), com transformações martensíticas reversíveis (TMR), submetida a tratamentos termo-cíclicos (TTC) sob carga, num intervalo que abrange as temperaturas críticas de TMR. A liga foi fabricada pela empresa "Memory Crystals Group", na Rússia. Neste estudo, maior atenção foi dada às alterações da estrutura e histerese térmica, associada a TMR. As temperaturas críticas de TMR e a grandeza da histerese térmica foram determinadas a partir da análise por calorimetria exploratória diferencial. Na caracterização estrutural da liga foram envolvidas a microscopia ótica e a difração de raios-X. Para realizar os TTC sob carga compressiva, foi desenvolvido um dispositivo especial. As análises evidenciaram uma diminuição nos intervalos críticos de TMR e na histerese térmica, até 13 oC, favorecendo a TMR. Esta tendência torna-se mais evidente com o aumento dos ciclos térmicos aplicados. Após TTC sob carga de 0,5 kg e aquecimento a partir de 0 oC, a TMR reversa

In this work, a monocrystalline Cu-13.5 wt% Al – 4.0 wt% Ni alloy exhibiting reversible martensitic transformation (RMT) was studied. The alloy was submitted to thermo-cycling treatment (TCT) under load in na interval that covers the critical temperatures associated with RMT. The Russian firm “Memory Crystals Group” was responsible for the fabrication of the alloy. In this study, a greater attention was paid to the RMT structural changes and thermal hysteresis. These, together with the critical temperatures were investigated by means of differential exploratory calorimetric analysis. Optical microscopy and X-ray diffraction were used to characterize the alloy structure. A special device was developed to allow for the TCT analysis under compressive load. This analysis showed a decrease in both the RMT intervals and the thermal hysteresis up to 13°C. It was concluded that the TCT under load favors the RMT, which becomes more evident with the number of applied cycles. After the TCT under a 0,5 kg load and heating starting from 0°C, a reverse RMT related to y’1 -> R -> B1 begins, on heating, at lower temperatures and, on cooling, at 90°C. The direct RMT, y’1 -> R -> B1, begins at higher temperatures. The applied load participates in both the structure re-orientation and the stabilization of R phase, which is coherent with y’1 and B1.

Keywords

Liga monocristalina Cu-Al-Ni; Transformações martensíticas reversíveis; Tratamentos termo-cíclicos; Histerese térmica.

Monocrystalline Cu-Al-Ni alloy, Reversible martensitic Transformations, thermo-cycling treatments, thermal hysteresis.