In-situ TOF neutron diffraction studies of cyclic softening in superelasticity of a NiFeGaCo shape memory alloy

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:680

Article

Yang, H.^1,2,3  Yu, D.^2,4  Chen, Y.²  Mu, J.¹  Wang, Y. D.^1,5  An, K.² 

[1] Northeastern Univ, Key Lab Anisotropy & Texture Mat, Shenyang 110819, Peoples R China

[2] Oak Ridge Natl Lab, Chem Engn Mat Div, Oak Ridge, TN 37831 USA

[3] Univ Tennessee, Dept Mat Sci & Engn, Knoxville, TN 37996 USA

[4] Tianjin Univ, Sch Chem Engn & Technol, Tianjin 300072, Peoples R China

[5] Univ Sci & Technol Beijing, State Key Lab Adv Met & Mat, Beijing 100083, Peoples R China

关键词: Ferromagnetic shape memory alloy;    Ni-Fe-Ga-Co;    Superelasticity;    Neutron diffraction;    Stress-induced martensitic transformation;   

DOI  :  10.1016/j.msea.2016.10.078

来源: Elsevier

【 摘 要 】

Real-time in-situ neutron diffraction was conducted during uniaxial cycling compression of a Ni(49.)3Fe(13)Ga(27)C(05.7) shape memory alloy to explore the mechanism on its superelasticity at room temperature, which was manifested by the almost recoverable large strains and the apparent cyclic softening. Based on the Rietveld refinements, the real-time evolution of volume fraction of martensite was in-situ monitored, indicating the incremental amount of residual martensite with increasing load cycles. Real-time changes in intensities and lattice strains of {hkl} reflections for individual phase were obtained through fitting individual peaks, which reveal the quantitative information on phase transformation kinetics as a function of grain orientation and stress/strain partitioning. Moreover, a large compressive residual stress was evidenced in the parent phase, which should be balanced by the residual martensite after the second unloading cycle. The large compressive residual stress found in the parent austenite phase may account for the cyclic effect on critical stress required for triggering the martensitic transformation in the subsequent loading.

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