Elevated Temperature Deformation Behavior of Dispersion-Strengthened Al and Al-Li-Mg Alloys

摘要

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 deg C and strain rates of 5 X 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 TiO_2 dispersoids, and (c) 10 nm diameter Al_2O_3 dispersoids have been studied. The effect of varying the volume fraction of the TiO_2 dispersoids and adding alloying additions of Mg and Li to the matrix Al have been investigated. In addition, the TiO_2 particles are shown to have reacted to form Al_3Ti. An adaptation to the detachment model of Rosler 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.