Effect of copper concentration and annealing temperature on the structure and mechanical properties of Al–2wt.%Mn ingots and cold rolled sheets

Abstract

This study focuses on the development of new Al–Cu–Mn alloys with enhanced strength and heat resistance achieved without hightemperature exposure. Seven alloys were considered including ones containing permanent Mn content of 2 % and variable Cu content of 0– 4 %. It was found that ~ 2 % Mn is completely dissolved in the solid solution of aluminum, while copper in the cast structure is distributed between the solid solution of aluminum and Al 2 Cu eutectic phase inclusions. It was experimentally established that when the copper content is 2 and 3 %, the solid solution of aluminum contains approximately the same amount of copper – up to 1.5 %. The deformation plasticity of experimental alloys in the cold rolling mode with the reduction rate of 80 and 95 % was investigated. It was shown that no preliminary treatment is required for alloys containing up to 3 % Cu as they feature high rolling workability. Then, the effect of heat treatment in the annealing temperature range of 200–600 °C on the structural and phase parameters of the alloys was studied. Alloy hardening in the process of multistage annealing by means of hardness measurement was analyzed. The data obtained allowed us to determine the influence of copper and analyze the thermal stability of model alloys. Tensile tests of cold rolled sheets with a thickness of 0.5 mm with a reduction rate of 95 % of alloys containing 2 and 3 % copper showed high performance. Particularly, the alloy containing 3 % Cu has strength compatible with that of the 1201 alloy in the T6 state.