SUPERPLASTICITY OF MEDIUM STRENGTH DEFORMABLE ALUMINUM ALLOY 1201

Abstract

The article presents the results of an experimental study of the superplasticity of medium-strength deformable aluminum alloy 1201 of the Al-Cu-Mn system, which is used for the manufacture of welded containers, cylinders and other constructions intended for operation at low (up to – 269 °C), room and elevated temperatures. The temperature-strain rate conditions under which samples of alloy 1201, deformed in the creep mode at high homologous temperatures, exhibit the effect of structural superplasticity have been determined, and the structural changes that occur in the working parts of samples of this alloy during superplastic deformation have been investigated. The influence of the phase composition on the structural state of the samples and on the stability of their grain structure at high homologous temperatures was analyzed. The average grain size in samples of alloy 1201 prepared for mechanical testing is 20 μm. This indicates that under industrial production conditions, the entire volume of deformed semi-finished products of alloy 1201, from which samples for mechanical testing were made, underwent almost complete recrystallization, the purpose of which was the formation of a fine-grained grain structure. During deformation of samples at high homologous temperatures, there is no increase in the average grain size. It has been established that during superplastic deformation in samples of alloy 1201, intensive grain boundary sliding occurs, and grain boundary cavities also nucleate, grow, and coalesce. Their origin is probably associated with the relaxation of local stresses that arise during grain boundary sliding at triple grain junctions, as well as near clusters of intermetallic particles localized at grain boundaries. During superplastic deformation, grain boundary cavities likely create the opportunity for grains to perform intensive movements in the working part of the sample by grain boundary sliding. The accumulation of grain boundary cavities during superplastic deformation in the working part of the samples and their merging into magistral cracks leads to the failure of the samples, which occurs without neck formation.