DYNAMIC SOFTENING MECHANISM OF 2099 ALLOY DURING HOT DEFORMATION PROCESS

Abstract

Dynamic softening mechanism of 2099 alloy was investigated by isothermal compression tests,thermal activation parameters calculation and comparison, EBSD and TEM techniques. On the basis of ZenerHollomon parameter(Z) and deformation temperature(T), combining thermal activation parameters and microstructures analysis, the softening mechanism of 2099 alloy during hot deformation has been proposed. Dislocation cross slip plays a dominant role under the conditions of lnZ≥35.5 and T≤380 ℃. While, deformation mechanisms such as cross slip, climb of dislocation and unzipping of attractive junction play a joint role when lnZ≤37.4 and T≥340 ℃. Particularly, dynamic recrystallization occurred in the range of lnZ≤35.1 and T≥420 ℃, cross slip, climb and unzipping of dislocation and dynamic recrystallization are the main softening mechanisms in this condition.Dynamic recrystallization nucleation mechanisms are constituted of grain boundaries bulging nucleation and subgrain rotated induced nucleation, and the latter becomes more significant with increasing temperature and decreasing strain rate.