A new kinetics model of dynamic recrystallization for magnesium alloy AZ31B
Highlights
► In this study, the new kinetics model of DRX was built. ► The model reflects slow-beginning, rapid-increasing, slow-rising-to-balance phases. ► The strain ɛ3 is of great significance to optimize industrial processes. ► This new kinetics model of DRX has fewer parameters—kv except ɛc and ɛ0.5. ► The calculated results are in good agreement with the experimental data.
Introduction
The objective of metal forming is not only to form desired shapes and dimensions, but to obtain superior mechanical properties as well. The in-depth study on microstructural evolutions of hot deformation will be helpful to determine the optimal process parameters of hot working. Dynamic recrystallization (DRX) is considered as one of the most important microstructural evolution mechanisms, which is beneficial to obtain fine metallurgical structures, eliminate defects and improve mechanical properties of products. With the development of computer technologies and numerical simulations, it is crucial to model the microstructural evolutions and predict the microstructural changes. In the last three decades, many researchers have proposed some microstructural evolution models suitable for different materials. Although the DRX kinetics models proposed by researchers have some differences in parameters and forms, they are all based on the Avrami function. By analyzing several typical and highly influential models, a new DRX kinetics model, which is able to more reasonably demonstrate the velocity of DRX was built. The new DRX kinetics model is in accord with the usual way that DRX develops, and has fewer parameters. Through the new model the most favorite and economic strain corresponding to fine and uniform grains is able to be obtained at a given temperature and strain rate, which is significant to design and optimize hot deformation processes.
Section snippets
Reviews and discussions
Sellars and co-workers [1], [2] conducted pioneering research on microstructural evolution on the basis of a great quantity of Gleeble thermomechanical tests, and a series of models which cover almost all the probable physical metallurgical phenomena related to DRX, static recrystallization (SRX) and grain growth were put forward. The DRX kinetics model proposed by Sellars based on Avrami function is as follows:where XDRX is the dynamically recrystallized volume fraction, t
A new kinetics model of DRX
The characteristics of DRX are as follows: the dynamically recrystallized volume fraction equals zero when the strain is smaller than the critical strain, and the maximum of the dynamically recrystallized volume fraction equals 1; once the strain exceeds the critical strain, the dynamically recrystallized volume fraction first slowly increases, and then rapidly increases, at last slowly increases. Based on these characteristics of DRX process and the feature of the limit of exponent function,
Material and experimental results
Take magnesium alloy AZ31B (Mg–3%Al–1%Zn) for example, the diameter of the sample is 10 mm and the length is 15 mm. The isothermal compression tests were performed on the thermomechanical simulator Gleeble-1500 at the temperatures ranging from 523 K to 673 K and at the strain rates 0.001 s−1, 0.01 s−1, 0.1 s−1 and 1 s−1. The maximum true strain is 1.0. The stress–strain curves obtained from the tests are shown in Fig. 3.
According to Fig. 3, the characteristics of AZ31B stress–strain curves are
Determination of parameters and verification
Bergstrom [11] pointed out that for the material characterized by DRX, the flow stress can be written bywhere XDRX is the dynamically recrystallized volume fraction; σp and σss are the peak stress and the steady-state stress, respectively. XDRX can be calculated according to the flow stress curves by converting Eq. (17) into the following form:
By Eq. (7), the following form can be obtained.
Take log of both sides of Eq. (19):
Conclusions
The following conclusions can be drawn:
- 1)
The new kinetics model of DRX reflects the ‘slow–rapid–slow’ property of DRX development. According to the new model, the development process of DRX can be divided into three phases: slow-beginning phase, rapid-increasing phase and slow-rising-to-balance phase. The strain at the turning moment between the second phase and the third one can be considered as the most appropriate and economic strain that guarantees fine grains and saves energy consumption.
- 2)
Acknowledgements
This work was supported by the National Basic Research Program of China under Grant No. 50905110.
References (21)
- et al.
Journal of Materials Processing Technology
(1995) - et al.
Materials Science and Engineering A
(2003) - et al.
Materials Science and Engineering A
(2001) - et al.
Mechanics Research Communications
(2003) - et al.
Materials Science and Engineering
(2003) - et al.
Materials Science and Engineering
(2001) - et al.
Journal of Materials Processing Technology
(2003) - et al.
Scripta Materialia
(2000) - et al.
Computational Materials Science (SCI/EI)
(2008) Materials Science and Technology
(1990)
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