| Popis: |
In this investigation, the general problem of the mechanical behaviour of partially recrystallized 8090-T851 Al-Li plate is posed. Tension and fracture toughness (J{sub IC} and J-R curves) tests were performed in the LT and TL directions. Owing to the fact that a strong morphologic and crystallographic texture is present across the thickness, emphasis has been given to the comparison between plate surface and core. The results of tensile tests indicate a sligth in-plane anisotropy, whereas a strong difference was detected between surface and core, the latter resulting much more resistent. On the contrary, J{sub IC} results and J-R curve of the surface and core are surprisingly close, whereas noticeable differences occur between LT and TL directions. The distribution of the strength across the thickness is then explained in terms of texture. More difficult is the explaination of the toughness data, which are related to the microstructure in a complex way, mainly through delaminations along high angle grain boundaries. The paper concludes with a thorough discussion on the possible microstructural reasons of the fracture toughness trends, combining delamination with constraint effects. (orig.) |
