TC4合金热变形过程中多形态α相的动态再结晶行为

Dynamic Recrystallization Behavior of Multi-modal α Phases in TC4 Alloy During Hot Deformation

摘要:

以宽幅热轧开坯态TC4合金为研究对象，采用Gleeble热模拟试验系统，在变形温度1173 K、应变速率10、0.01 s?¹条件下，系统研究了2种典型初始组织（全层片组织和等轴–层片双态组织）的热变形响应及其动态再结晶行为。同时，构建了相场-晶体塑性耦合模型，对不同初始组织条件下α/β两相的应力–应变分配及位错密度演化进行了多尺度模拟，探讨了初始组织构型对α相动态再结晶行为的影响。结果表明，在高应变速率（10 s?1）条件下变形60%，全层片组织中α相发生了显著的动态再结晶，获得了平均尺寸为0.58 μm的均匀细晶组织；而双态组织中，仅部分层片α相呈现局部再结晶特征，等轴α相则主要经历了动态回复过程。相比之下，双态组织需更大的变形量才能同时激活等轴α相与层片α相的动态再结晶。这种不连续再结晶行为归因于等轴α相与层片α相在协同变形过程中应力–应变分配的差异，从而影响了两者的位错积累与亚晶结构的形成，最终改变了动态再结晶的驱动力条件。

Abstract:

The hot deformation response and dynamic recrystallization behavior of two representative initial microstructures (a fully lamellar microstructure and an equiaxed-lamellar bi-modal microstructure) were systematically investigated in a wide-width hot-rolled bloom TC4 alloy using a Gleeble thermal simulation testing system at deformation temperature of 1173 K and strain rates of 10 and 0.01 s?1. Meanwhile, a coupled phase-field and crystal plasticity model was developed to simulate the stress-strain distribution and dislocation density evolution in the α/β phases under different initial microstructural conditions. This model was used to examine how initial microstructure configurations influence the dynamic recrystallization behavior of the α phase. The results indicate that under a high strain rate of 10 s?1 and the deformation of 60%, the fully lamellar microstructure undergoes significant dynamic recrystallization in the α phase, resulting in a uniform fine-grained structure with an average grain size of 0.58 μm. In contrast, in the bi-modal structure, only part of the lamellar α phase exhibits localized recrystallization, while the equiaxed α phase primarily undergoes dynamic recovery. Compared with the fully lamellar structure, the bi-modal microstructure requires greater deformation to activate dynamic recrystallization in both the equiaxed and lamellar α phases. This discontinuous recrystallization behavior is attributed to differences in stress-strain distribution between the equiaxed and lamellar α phases during concurrent deformation. These differences influence dislocation accumulation and subgrain formation, ultimately altering the driving force conditions for dynamic recrystallization.