Correlative SANS and TEM investigation on precipitation kinetics of H-phase in Ni50.3Ti29.7Hf20 high temperature shape memory alloy

JOURNAL OF ALLOYS AND COMPOUNDS

卷:779

Article

Prasher, Meenu^1,4  Sen, Debasis^2,4  Bahadur, J.²  Tewari, R.^3,4  Krishnan, Madangopal¹ 

[1] Bhabha Atom Res Ctr, Glass & Adv Mat Div, Mumbai 400085, Maharashtra, India

[2] Bhabha Atom Res Ctr, Solid State Phys Div, Mumbai 400085, Maharashtra, India

[3] Bhabha Atom Res Ctr, Mat Sci Div, Mumbai 400085, Maharashtra, India

[4] Homi Bhabha Natl Inst, Mumbai 400094, Maharashtra, India

关键词: Shape memory alloys;    Phase transformations;    Precipitation kinetics;    Transmission electron microscopy;    Small-angle neutron scattering;   

DOI  :  10.1016/j.jallcom.2018.11.303

来源: Elsevier

【 摘 要 】

NiTiHf alloys are emerging as promising candidates for high-temperature shape memory actuator applications. The H-phase precipitation in these alloys significantly influences their mechanical strength and transformation temperatures. In this paper, we report a complementary study using time-resolved Small-Angle Neutron Scattering (SANS) along with transmission electron microscopy, to probe the H-phase evolution as a function of aging conditions in the Ni50.3Ti29.7Hf20 alloy. While, electron microscopy provided direct structural information about the precipitates, SANS analysis allowed in probing quantitatively the temporal evolution growth and coarsening of H-phase. It is demonstrated that while the diffusion of Ni atoms in the matrix predominantly governs the growth regime, the coarsening kinetics is primarily controlled by Hf diffusion. Further, relatively sluggish coarsening of the H-phase in this alloy, as compared to Ni4Ti3 precipitates in Ni-rich binary NiTi alloy, has been attributed to the slow migration of Hf in the matrix. (C) 2018 Elsevier B.V. All rights reserved.

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