The behavior of interaction between dislocation and T 1 plate was observed and analyzed by means of TEM technique in Al Li alloys of 2090 and 2090+Ce. The observation results show that the interaction between dislocation and T 1 plate is a mix type of shearing and Orowan looping, and the physical models are established by theory of precipitates strengthening. The results of calculation illustrate that the contribution of T 1 plate is up 30%～60% to the overall critical resolved shear stress (CRSS). The role of T 1 plate is enhanced with aging time in the material aged 3～48 h at 190℃, but this enhancing effect becomes gentle on overaged condition. The strengthening effects of T 1 plate in 2090 and 2090+Ce alloys are little different on under aged condition, but the strengthening effects of T 1 precipitates in alloy 2090+Ce is little bigger than that of 2090 on overaged condition, especially the cutting mechanism is only considered. The difference between strengthening effects of matrix in two alloys is about 3.2 MPa on underaged condition and 8.7 MPa or so on overaged condition.
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