The mechanism of negative linear thermal expansion behavior of cold-rolled Ti-34Nb alloy
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The mechanism of negative linear thermal expansion behavior of cold-rolled Ti-34Nb alloy Xiangwei Wu1, Wenqian Zou1, Jindu Huang2, Yulong Wu1, Cong Luo1, Chunbo Lan1, and Feng Chen1,2,* 1 2
Department of Materials Science and Engineering, Southeast University, Nanjing 211189, China Jiangsu Key Laboratory of Advanced Metallic Materials, Southeast University, Nanjing 211189, China
Received: 24 May 2020
ABSTRACT
Accepted: 13 November 2020
The mechanism of negative linear thermal expansion (NLTE) of Ti-34Nb (wt.%) alloy after 90% cold rolling is investigated by X-ray diffraction, thermal expansion and transmission electron microscopy. From the results, it is observed that 90% cold-rolled Ti-34Nb alloy is composed of b and a00 (Martensite) phases with the existence of \ 110 [ b and \ 010 [ a00 textures along rolling direction (RD). The cyclic thermal expansion, XRD and TEM studies show that when the thermal cycle temperature is at 100 °C, the RD of 90% cold-rolled Ti-34Nb alloy performs a reversible NLTE, which gradually weakens when thermal cycle temperature is at 300 °C, attributing to the gradual decomposition of a00 -phase. When thermal cycle temperature rises to 380 °C, the reversible NLTE disappears and turns into positive linear thermal expansion, meanwhile, a00 -phase decomposes completely. Based on the formation of b and a00 textures by cold rolling and a00 $ b thermo-reversible transformation mechanism, the NLTE mechanism of 90% cold-rolled Ti-34Nb alloy is successfully explained. Moreover, according to the present results, a novel strategy is proposed to tailoring the negative coefficient of linear thermal expansion by changing a00 content, which improves the application potential of Ti alloys.
Published online: 1 December 2020
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
Introduction The temperature dependence of length or volume, usually called thermal expansion, is an intrinsic nature of metallic materials caused by the change of average interatomic distance [1]. Metallic materials at
work are usually influenced by a large temperature variation or temperature gradient, and it is easy to produce thermal stress, which limits its application. For instance, the difference in coefficients of thermal expansion between substrates and thin films produces internal stress, which affects the physical, electrical and thermal properties of thin films [2–4]. In
Handling Editor: David Balloy.
Address correspondence to E-mail: [email protected]
https://doi.org/10.1007/s10853-020-05574-7
J Mater Sci (2021) 56:5190–5200
bridges, rails and pipelines, thermal expansion has to be compensated through expansion joints. Fortunately, these problems can be well solved by compounding positive thermal expansion materials with negative thermal expansion materials. In addition, the composite can also be used to fabricate temperature sensitive components. Therefore, in recent years, materials with negative thermal expansion (negative coefficient of thermal expansion) have attracted considerable a
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