Elevated temperature deformation behavior of dispersion-strengthened Al and Al-Li-Mg alloys

Abstract

A model describing the behavior of dispersion-strengthened aluminum alloys, when subjected to elevated temperature plastic deformation, is presented. The aims are twofold:

• • to use the model for extrapolation of laboratory data to predict behavior under service conditions where the strain rate is extremely low (<10⁻⁹ s⁻¹); and

• • to design and fabricate materials having specific elevated temperature properties based on microstructural predictions from the model.

The results of constant strain-rate compression tests covering a range of temperatures from 250 to 550 °C and strain rates of 5 × 10⁻⁵ to 10⁻¹ s⁻¹ are presented in conjunction with microstructural investigations using transmission electron microscopy (TEM) and x-ray diffraction. Materials mechanically alloyed with (a) no dispersoids, (b) 23 nm radius TiO₂ dispersoids, and (c) 10 nm diameter Al₂O₃ dispersoids have been studied. The effect of varying the volume fraction of the TiO₂ dispersoids and adding alloying additions of Mg and Li to the matrix Al have been investigated. In addition, the TiO₂ particles are shown to have reacted to form Al₃Ti. An adaptation to the detachment model of Rösler and Arzt has been proposed to account for the behavior of these types of materials and to enable accurate prediction of deformation behavior at elevated temperatures and low strain rates.