An improved kinetics model to describe dynamic recrystallization behavior under inconstant deformation conditions
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Yong-Cheng Linb) School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China; State Key Laboratory of High Performance Complex Manufacturing, Changsha 410083, China; and Light Alloy Research Institute of Central South University, Changsha 410083, China
Wu-Quan Yuan School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China; and State Key Laboratory of High Performance Complex Manufacturing, Changsha 410083, China (Received 11 July 2016; accepted 19 August 2016)
The classical dynamic recrystallization (DRX) kinetics models, such as Avrami equation, are often used to describe the DRX behaviors of alloys. However, it is found that the classical DRX kinetics models cannot be directly applied to evaluate DRX volume fractions under inconstant deformation conditions, such as at fluctuant deformation temperature and strain rate. It obviously limits their application in the practical industrial production. Therefore, an improved DRX kinetics model is proposed based on the hypothesis that the derivatives of DRX volume fraction with respect to strain only depends on the current deformation temperature, strain rate, and DRX volume fraction. To verify the improved DRX kinetics model, the hot compressive tests in which the strain rate is inconstant are carried out on a solution-treated Ni-based superalloy. Experimental results indicate that the improved DRX kinetics model can well predict the DRX behavior under inconstant deformation conditions.
I. INTRODUCTION
Dynamic recrystallization (DRX) is one of most important microstructural evolution mechanisms for most of metals and alloys during hot deformation, such as forging. During DRX, the initial coarse-grains are gradually replaced by fine DRX grains. The final microstructures of forgings greatly depend on the DRX volume fraction and grain size.1,2 Incomplete DRX, where the DRX volume fraction is less than 95%, will result in serious mixed structures with fine and coarse grains. This is not permitted or expected since the mixed structure will seriously deteriorate the mechanical properties for most materials. Therefore, it is very significant to precisely predict and control the DRX volume fraction of forgings after hot deformation. The DRX kinetics model is essential to predict and control the DRX volume fraction of forgings. In recent decades, some efforts have been made to investigate the DRX behaviors and kinetics models of various metals
Contributing Editor: Mathias Göken Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2016.325
and alloys, such as Nb-steels,3,4 Aermet100 steel,5 38MnVS6 Steel,6 42CrMo steel,7 a low carbon vanadium-nitride microalloyed steel,8 SCM435 steel,9 300M steel,10 17-4 PH stainless steel,11 X70 pipeline steel,12 titanium-modified austenitic stainless steel,13 410 martensitic stainless steel,14 superaustenitic stainless steel,15 304 stainless steel,16–18 martensitic stainless steel,19 high purity and ul
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