初始组织对Ti-6Al-4V合金高温变形机制影响研究

Effect of initial microstructure on hot deformation behavior of Ti-6Al-4V alloy

研究了两种不同初始组织(魏氏组织、马氏体组织)Ti-6Al-4V合金在温度区间为700~750℃,应变速率为10^(-3)~1s^(-1)之间的高温变形行为。结果表明:初始组织对Ti-6Al-4V合金高温变形行为有着重要影响,初始魏氏组织Ti-6Al-4V合金主要发生了绝热剪切变形,在试样内部形成了绝热剪切带,绝热剪切带的密度随着温度上升和应变速率下降而减小;α′马氏体组织Ti-6Al-4V合金主要发生了稳态变形,在试样内形成了晶粒尺寸在亚微米级甚至纳米级的超细晶组织,晶粒尺寸和组织均匀性随着温度升高和应变速率减小而增大。α′马氏体组织的晶粒细化机制主要是连续动态再结晶,α′/α+β相变过程为再结晶的发生提供了重要的驱动力。

The hot deformation behavior and microstructural evolution were investigated during subtransus hot deformation of a Ti-6 Al-4 Valloy with two initial microstructures（Widmansttten microstructure andα′martensitic microstructure）by compressive deformation in a Gleeble simulator.When deformed at a temperature of 700 ℃ and750 ℃,specimens with a Widmansttten microstructure exhibited flow instability.These microstructures exhibited flow localization bands due to the adiabatic conditions and the bands became diffused with increasing temperatures and decreasing strain rates.Specimens withα′martensitic microstructure exhibited extensive flow softening,especially,a homogeneous ultra-fine grained structure was achieved at all deformation conditions.The new ultrafine grains mainly formed through the process of continuous dynamic recrystallization（CDRX）.The phase transformation ofα′/α＋βwas strongly contributed to the microstructure refinement.