Microstructure and Texture Evolution in a Post-dynamic Recrystallized Titanium During Annealing, Monotonic and Cyclic Lo
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, X.-C. ZHANG, and S.-T. TU are with the Key Laboratory of Pressure Systems and Safety, Ministry of Education, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, P.R. China. Contact e-mail: [email protected] B. CHEN is with the School of Engineering, University of Leicester, Leicester, LE1 7RH, UK. Contact e-mail: [email protected] Z.-G. ZHENG is with the College of Mechanical Engineering, Guangxi University, Nanning 530004, P.R. China. B. GUAN is with the National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, P.R. China. Manuscript submitted July 12, 2020; accepted October 15, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS A
Graphical Abstract
https://doi.org/10.1007/s11661-020-06071-x The Author(s) 2020
I.
INTRODUCTION
THE generic term recrystallization describes the replacement of cold worked microstructure by forming new grains during annealing at temperatures of ‡ 0.5Tm. This process is referred to as discontinuous static recrystallization. By contrast, discontinuous dynamic recrystallization (dDRX) occurs during high-temperature straining. For both cases, recrystallized grains co-exist with the deformed ones, hence a discontinuous process. The recrystallization mechanism was studied for several decades and a thorough review of the literature was published in 1997.[1] Since then electron backscattered diffraction (EBSD) technique has become widespread and it enables mapping crystallographic orientations in a large number of grains with much reduced time compared to transmission electron microscopy (TEM). The paper published in 2014[2] provided a comprehensive review on two types of dynamic recrystallization: dDRX and continuous dynamic recrystallization (cDRX). A later review paper[3] considered the geometric DRX in addition to the above two. The evolving recrystallization terms can be attributed to the expansion of processing methods, in particular those arising from severe plastic deformation, SPD.[2] The SPD-induced ultrafine grain (UFG) microstructure can be characterized by the gradual transformation of low-angle into high-angle grain boundaries (LAGBs to HAGBs), that is the essence of cDRX. The dynamic UFG formation is accompanied by a dramatic decrease in dislocation density at the grain interior, while the
boundaries are in non-equilibrium state.[4] Over the last decades, much improved knowledge has been gained about the creation of UFG microstructure and the underlying cDRX mechanism.[5] However, the post-dynamic recrystallization behavior of UFG materials has not been explored very much.[2] The annealing behavior was examined on a range of UFG materials that included Cu, Type 304 stainless steel, Ni, Al and Mg.[2] It can be concluded that continuous static recrystallization (cSRX) mechanism was responsible for the grain growth. Compared to the cubic materials, much fewer studies on hexagonal close packed (hcp) materials (hot-deformed AZ31 Mg[6, 7]) have been published to date. Further
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