In this work stress-induced microstructural transitions and crack initiation and growth mechanisms in a near equiatomic NiTi shape memory alloy have been analyzed, by means of both X-ray diffraction (XRD) and scanning electron microscopy (SEM) investigations. In particular, miniaturized dog-bone shaped specimens and a special testing machine have been used, which allow in situ XRD and SEM investigations during mechanical loading. Direct and reverse stress-induced phase transition mechanisms, between the parent austenitic phase and the product martensitic one, have been captured by XRD while crack initiation and propagation mechanisms have been observed by means of SEM investigations. These analyses revealed that stress-induced transformations occurs near the crack tip, as a consequence of the highly localized stress, which significantly affect the crack propagation mechanisms with respect to common metallic alloys. In fact, blunting does not occurs during mechanical loading and, in addition, complete crack closure is observed during unloading, as a consequence of the reverse transformation from product to parent phase. (C) 2013 Elsevier Ltd. All rights reserved.

Cyclic microstructural transitions and fracture micromechanisms in a near equiatomic NiTi alloy

MALETTA, Carmine;
2014-01-01

Abstract

In this work stress-induced microstructural transitions and crack initiation and growth mechanisms in a near equiatomic NiTi shape memory alloy have been analyzed, by means of both X-ray diffraction (XRD) and scanning electron microscopy (SEM) investigations. In particular, miniaturized dog-bone shaped specimens and a special testing machine have been used, which allow in situ XRD and SEM investigations during mechanical loading. Direct and reverse stress-induced phase transition mechanisms, between the parent austenitic phase and the product martensitic one, have been captured by XRD while crack initiation and propagation mechanisms have been observed by means of SEM investigations. These analyses revealed that stress-induced transformations occurs near the crack tip, as a consequence of the highly localized stress, which significantly affect the crack propagation mechanisms with respect to common metallic alloys. In fact, blunting does not occurs during mechanical loading and, in addition, complete crack closure is observed during unloading, as a consequence of the reverse transformation from product to parent phase. (C) 2013 Elsevier Ltd. All rights reserved.
2014
Fracture; Microstructure; NiTi; SMA
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11770/139157
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 31
  • ???jsp.display-item.citation.isi??? 24
social impact