Ti-24Al-15Nb-1.5Mo合金近等温变形时的平均流动应力及组织演化

Average Flow Stress and Microstructure Evolution during Near Isothermal Deformation of Ti-24Al-15Nb-1.5Mo Alloy

研究了Ti-24Al-15Nb-1.5Mo合金在近等温条件下变形时的平均流动应力及组织演化。结果表明:应变速率对合金的力学行为有着显著的影响。在任一变形温度,随着应变速率的增大,平均流动应力明显增大。在变形过程中,变形温度对初生α2相晶粒的尺寸及体积分数有着较大的影响,随着变形温度的升高,其晶粒尺寸逐渐增大、体积分数逐渐减少。应变速率对初生α2相体积分数影响不大,但对其形态和尺寸有一定的影响。较高的应变速率使动态再结晶晶粒来不及长大、相界迁移合并没有时间进行,因而有利于细化晶粒。随着变形程度的提高,晶格畸变能及动态再结晶体积分数增加,使得晶粒细化程度有所增加。

The average flow stress and microstructure evolution during near isothermal deformation of Ti-24Al-15Nb-1.5Mo alloy have been investigated. The results show that the strain rate has a significant effect on the mechanical behavior of the alloy. At any deformation temperature, the average flow stress of the alloy increases with the increasing of strain rate. The deformation temperature has a significant influence on the grain size and volume fraction of the primary α2 phase, which grain size increases and volume fraction decreases with the increasing of temperature. Influence of the strain rate on the volume fraction of the primary α2 phase can be neglect, but it has a certain influence on the morphology and size of the α2 primary phase grain. The reason is that it has no enough time for the grains occurring dynamic recrystallization to grow up, and it has also no enough time to merge and migrate the phase boundary when the alloy is deformed with higher strain rate, which is advantage for the grain refinement. With increasing reduction, the distortion energy of the lattice and the volume fraction of the grains occurring dynamic recrystallization increase, which results in the increase of refining degree of the grains.