Abstract
The dynamic recrystallization behavior of as-cast Ti-46.5Al-3Ta-2Cr-0.2W alloy during isothermal compression process with nominal deformation of 50% and strain rates from 0.01s to 1s was investigated by electron microscopy. The results showed that the deformation mechanism of this alloy can be concluded as grain boundary sliding and mechanical twins, which induce the final dynamic recrystallization. The phase boundary bulging was found to be the major nucleation mechanism responsible for the lamellar globularization and the formation of recrystallized γ grains inside the lamellar colony under the high strain rate. The recrystallized γ grains induced by the twinning is the main mechanism for refining α2 lamellar microstructures under low strain rate.
Highlights
It is well known that the processes such as dynamic recovery (DRV), dynamic recrystallization (DRX), postdynamic recrystallization (MDRX), static recovery (SRV), static recrystallization (SRX), and grain growth may each affect the final microstructure of metals that is produced during thermomechanical processing [1]
It can be considered as the γR grains in this alloy, so the globularized microstructure consisted of dynamically recrystallized grains, which contained a high density of dislocations and networks, plus equiaxed dislocation-free grain
This recrystallization initiate by subgrain rotation is currently recognized as a common DRX mechanism in the hot-working of metals, and is referral to as “CDRX” in the present alloy because the grain boundary migration did not occur in this stage
Summary
It is well known that the processes such as dynamic recovery (DRV), dynamic recrystallization (DRX), postdynamic recrystallization (MDRX), static recovery (SRV), static recrystallization (SRX), and grain growth may each affect the final microstructure of metals that is produced during thermomechanical processing [1]. The appearances of the DRX are roughly classified into two major types [5~6]: the discontinuous and continuous dynamic recrystallization (DDRX and CDRX) based on the relative importance of grain boundary bulging (BLG) and subgrain rotation (SGR) nucleation. Discontinuous dynamic recrystallization (DDRX) is characterized by a rapid migration of grain boundaries between dislocation-free nuclei and deformed grains [7~9]. Many researcher cared about the DDRX in based alloys with high SFE, only a few investigators have paid attention to that how the CDRX and DDRX form respectively with the strain rates and how they play a role in isothermal deformation mechanism by hot compression tests in TiAl based alloys
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