Effects of aging treatments on the fatigue resistance of superelastic NiTi wires

Silva, Jéssica Dornelas; Martins, Suzanny Cristina Soares; Lopes, Natália Isabel de Azevedo; Resende, Pedro Damas; Santos, Leandro Arruda; Buono, Vicente Tadeu Lopes

doi:10.1016/j.msea.2019.04.037

Cited by 13 publications

(15 citation statements)

References 20 publications

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“…The samples with an initially dual-phase structure presented intermediate fatigue resistance. These results are in agreement with previous tests at 4 °C for samples heat-treated in different conditions [14]: the samples initially constituted by the R-phase presented much higher fatigue resistance at 4% strain than an initially austenitic structure.…”

Section: Discussionsupporting

confidence: 93%

“…In this manner, the detected DSC peaks are identified on the chart in accordance to Refs. [14,17,25,27]. During cooling, the first peak refers to austenite (A) → R-phase (R) transformation and the second to the R-phase (R) → martensite (M) transformation.…”

Section: Resultsmentioning

confidence: 99%

“…While in the studies performed in Ref. [14], the samples with different microstructures were obtained by heattreatment in different temperatures-and hence, having different thermic histories, in this study the different initial microstructures were obtained by using different test temperatures. In such case, the effect of the test temperature must also be considered.…”

Section: Discussionmentioning

confidence: 99%

“…The superelastic wire is drawn and pickled in its initial state, being in a strain-hardened condition, as previously noted in Ref. [14].…”

Section: Methodsmentioning

confidence: 99%

“…In this context, recent studies have been made to evaluate some microstructural effects on the crack growth and fatigue life such as the effect of downsizing inclusions [8], grain size [9] and grain orientation around stress concentrators [10] as well as attempts to obtain analytical models to describe the non-linear fatigue behavior of these materials [11,12]. Previous works by these authors [13,14] have studied the effect of heat-treatments in different temperatures in a commercially available superelastic wire and it has been observed that the ones that promote precipitation of coherent Ti 3 Ni 4 particles and the formation of the R-phase in the working temperature provide good fatigue resistance in low-cycle fatigue. However, during a heat-treatment, other microstructural changes can take place such as recovery and recrystallization processes, modifying the thermomechanical state of wires treated in different temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Effect of the initial phase constitution in the low-cycle fatigue of NiTi wires

Silva

Buono

2019

SN Appl. Sci.

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Vastly used due to their functional properties, NiTi shape memory alloys have mechanical properties and fatigue resistance known to be strongly affected by their thermomechanical state. In this work, the goal was to evaluate the fatigue resistance of near equiatomic Ni-rich NiTi heat treated wires in different tests temperature. In this manner, it was possible to evaluate the phase constitution effect on the fatigue resistance with a fixed thermomechanical condition. For that, a heat treatment at 500 °C for 30 min was performed in initially superelastic wires in an argon atmosphere. DSC tests were performed in order to obtain the transformation temperatures and there different fatigue test temperatures were chosen according to the phase stability ranges. Rotating-bending fatigue tests took place in proper equipment at 4% maximum strain, evaluating the properties of structures constituted by the R-phase, austenite and R-phase + austenite, in each selected test temperature. The results showed that the R-phase presents higher low-cycle fatigue resistance than austenite and a fatigue mechanism was proposed.

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Section: Discussionsupporting

confidence: 93%