Thermal stability of nanostructure in adiabatic shear band of 2195 Al-Li alloy

Split Hopkinson pressure bar (SHPB) was used for dynamic loading in hat-shaped specimen of T6 peak aged 2195 aluminum-lithium alloy to get shear band, and the thermal stability of the nanostructure in the shear band was studied. The microstructures of the shear band before and after dynamic loading were investigated by TEM and OM. EBSD was used to investigate the evolution of the microstructure within the shear band after annealing at 100~400°C for 1 h. The results show that the adiabatic shear bands form in the shear zone under the dynamic loading, the grain diameter in shear band are about 50~100 nm with no precipitates. The grains size increases with annealing temperature increases, e.g. grain sizes grow up quickly from 0.22 μm at 300°C to 1.77 μm at 400°C. And the microhardness of the nanostructure decrease significantly at 300°C. It can be concluded that the critical temperature of the grain sharply grow for the nanostructure produced in this way is about 300°C.