The effect of plastic deformation on Al2CuLi (T 1) precipitation

The enhancement ofT ₁ precipitation in Al-Li-Cu alloys by plastic deformation prior to aging (that is, cold work) and the subsequent increase in alloy strength is investigated. The increased understanding of the role of matrix dislocations in the nucleation and growth ofT ₁ plates, discussed in the previous paper,^1] permits a detailed study of the phenomenon. In this paper, the effect of different levels of plastic strain on theT ₁ particle distributions as a function of aging time at 190 °C is quantified, and the subsequent influence on tensile properties is thereby described. The effect of plastic deformation is shown to decrease theT ₁ plate length and thickness, increase the number density by almost two orders of magnitude, increase the yield strength by 100 MPa, while simultaneously reaching peak strength in 20 pct of the time required without plastic deformation. Formerly Graduate Student, Department of Materials Science, University of Virginia,