On the microstructure and mechanical properties of a two-way shape memory NiTi/NiTiCu bi-layer diaphragm. (March 2020)

• Record Type: Journal Article
• Authors: Askari-Naeini, Farzad Ghazi; Taghizadeh, Milad; Mohri, Maryam; Nili-Ahmadabadi, Mahmoud
• Is Part Of: Materials & design. Volume 188(2020)
• Publication Date: 2020-03
• Subjects: Shape memory alloys -- Bi-layer diaphragm -- FEM simulation -- Diaphragmatic actuation -- Two-way shape memory effect; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2019.108464
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: In this research, a NiTi/NiTiCu bi-layer composite consist of austenitic and martensitic layers was made by the diffusion bonding method, to make a diaphragm to show two-way shape memory actuation. The initial phase of the single sheets and the quality of the bonding after diffusion annealing were investigated using X-ray diffraction (XRD) and microstructural analyses, respectively. The effects of applied force on both sides of the diaphragm were studied using loading-unloading steps in the bending test. The observations implied the dependence of mechanical response on the loading mode; pseudo-elastic displacement and thermal recovery showed various figures when the loading mode changes. For both the loading modes, interestingly, the bi-layer showed two-way shape memory behavior in a diaphragmatic mode at a certain amount of force, without any complicated thermomechanical process and training and just by one cycle of loading-unloading. However, the results illustrated a more extensive range of total displacement in which the bi-layer showed two-way shape memory behavior when the load applied on the austenitic side. The stress and strain profile in the cross-section of the diaphragm was studied using finite element simulation. The results could be useful in the design of diaphragms with two-way shape memory behavior. Graphical abstract: Unlabelled Image Highlights: The designed martensitic/austenitic bi-layer diaphragm showed a two-way shape memory effect by one loading-unloading cycle. When load applied on the austenitic side, the two-way shape memory effect started at a lower displacement level. When load applied on the martensitic side, the two-way shape memory effect started at a higher displacement level. The bi-layer was introduced as a capable material to show two-way SME for use as a diaphragm in micropump.