Branching of {110) twin boundaries in five-layered Ni-Mn-Ga bent single crystals. (5th June 2019)

• Record Type: Journal Article
• Authors: Chulist, R.; Straka, L.; Seiner, H.; Sozinov, A.; Schell, N.; Tokarski, T.
• Is Part Of: Materials & design. Volume 171(2019)
• Publication Date: 2019-06-05
• Subjects: NiMnGa -- Bending -- Twinning -- Interfacial misfit -- Continuum mechanics; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2019.107703
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Two bending tests around two perpendicular axes were applied to 10M Ni-Mn-Ga single crystals with five-layered modulated structure. The crystal structure and microstructure evolution were examined using synchrotron radiation and electron backscatter diffraction, respectively. The bend stress results in pseudoelasto-plastic strain due to {101) twins tapering. A close examination of the microstructure reveals an additional pattern indicating microstructural changes in the form of {110) twins. As bending proceeds the {110) twins branch undergoing a significant twin refinement. Additionally, an elastic change of lattice parameters is confirmed yielding a higher total pseudoelastic strain. Unloading restores the initial twin configuration removing a large amount of the {110) twin boundaries, however, this process is followed by incomplete recovery since the samples do not retain its original shape entirely. The paper underlines the differences in mechanism for bending around two perpendicular axes explaining the amount of strain observed under pseudoelastic deformation. Additionally, the results are discussed with respect to minimization of elastic energy due to twin refinement and branching as well as mobility of the {101) and {110) twin boundaries. Graphical abstract: Unlabelled Image Highlights: Twin tapering and elastic change of lattice parameters cause pseudoelastic effect with a large bending angle of 129°. The plastic-elastic response is explained by an equilibrium between distance of piled - up dislocations and twinning stress . Bending refines {110) twins in order to maintain the compatibility along the tapered {101) twins.