Review on globularization of titanium alloy with lamellar colony

Abstract

The globularization of titanium alloy with lamellar colony during hot working is an important way to obtain fine and homogeneous microstructure which has excellent mechanical properties. Because of its great technological importance, globularization has captured wide attention and much research. This paper conducts a systematic study on state of art on globularization of titanium alloy, which mainly includes globularization mechanism, prediction model and the effects of hot-working parameters and microstructure parameters. Firstly, the shortcomings of the well-known globularization mechanisms (dynamic recrystallization, boundary splitting, shearing mechanism and termination migration) were summarized. Moreover, the comparison and analysis of prediction models were accomplished through tabular form. In addition, the effects of hot-working parameters (strain, strain rate, temperature) and microstructure parameters (alpha/beta interface, geometry necessary dislocation and high temperature parent beta phase) were systematically summarized and analyzed. Meanwhile, this study also explores those difficulties and challenges faced by precise control on globularization. Finally, an outlook and development tendency of globularization of titanium alloy are also provided, which includes microstructure evolution of three-dimensional lamellar alpha, the relationship between lamellar colony and mechanical properties and the effect of severe plastic deformation on globularization.

Hot working behaviour of Ti–8Al–1Mo–1V alloy through the hot compression test

“…On the other hand, the deformation behaviour of α phase depends not only on the initial microstructure but also on the parameters such as deformation temperature, 6 strain rate 7 and true strain. 8,9 Similarly, the occurrence of flow softening due to dynamic recovery (DRV) 10 and recrystallisation (DRX) 11 of β phase and the dynamic phase transformation (DT) due to adiabatic heating [12][13][14] are additional challenges to study the hot rheological behaviour of Ti alloys at elevated temperatures. Hence, proper selection of the deformation parameters accompanied by an accurate examination of the rheological behaviour of alloy can be vital to optimise process and control the microstructural evolutions during hot deformation.…”

Correlation between Solution Treatment Temperature, MicroStructure, and Yield Strength of Forged Ti-17 Alloys

“…Because a globularized α microstructure exhibits better balance in terms of strength and ductility, formation processing and prediction models to induce globularization of the α phase have been extensively investigated [7][8][9][10][11]. A review paper on globularization indicates that the strain introduced during forging and the strain rate of deformation affect the kinetics of globularization of the lamellar structure [12]; specifically, higher strain and a lower strain rate promote globularization. The deformation temperature also affects the globularization mechanism in that a high deformation temperature promotes the formation of a granular α phase by dynamic recrystallization and a low deformation temperature promotes the formation of a granular α phase by boundary splitting [12].…”

“…The strain introduced by forging is nonuniform and therefore varies by position in forged materials [4,12]. Controlling the strain in forged materials requires an understanding of the processing.…”

Understanding the impact of microstructure on the response of titanium alloys to aging treatments

“…These findings are important to understand the superplastic behavior of α+β alloys in these conditions and for the continuous development of models to predict their flow behavior, aiming at the constant improvement of processing maps (HU et al, 2018;SESHACHARYULU et al, 2002). The dynamic globularization mechanism of the α phase with lamellar morphology is usually attributed to dynamic recrystallization (splitting of lamellae into necklace strings with similar orientation), but different globularization mechanisms have been proposed, such as boundary splitting (formation of sub-boundaries within lamellae with subsequent wedging of the β phase into the α/β interface, evolving to a globular morphology) and shearing mechanism (shearing of lamellae leading to dislocation migration and interface formation along shear lines, promoting globularization) ZHAN, 2020). The understanding of substructure evolution in colony α is critical for the development of advanced models for texture evolution and dynamic globularization, for example .…”

“…The understanding of substructure evolution in colony α is critical for the development of advanced models for texture evolution and dynamic globularization, for example . However, descriptions of these mechanisms are mostly qualitative, lacking quantitative description of microstructural features such as crystal and substructure orientation ZHAN, 2020). Moreover, a subject of growing interest during α+β processing is a dynamic reduction in the α phase volume fraction with respect to static conditions, whose mechanisms are not yet fully known .…”