Influence of cold rolling on the precipitation in an Al–Mn–Zr alloy

• The precipitation of α-Al(Mn,Fe)Si and Al3Zr dispersoids is affected by cold rolling reduction.
• The highest density of particles was found in the sheet cold rolled with 96% reduction.
• Some Al3Zr particles with L12 structure were identified by electron diffraction.

The aim of the experiments was to study the influence of the rolling reduction (39, 87, and 96%) on the size and distribution of secondary particles and recrystallization behaviour of Al–Mn sheets with Zr addition prepared by twin-roll casting (TRC) in the industrial conditions. Samples, cold rolled on a laboratory mill, were subjected to a two-step precipitation annealing. Their microstructure (grain structure, substructure, particle analysis) as well as mechanical and physical properties (microhardness, electrical conductivity, resisitivity) were then characterized. The material cold worked with 39% reduction shows a moderate decrease of microhardness due to recovery, while sheets cold worked with 87 and 96% reduction soften more due to recrystallization. Regardless of the cold rolling reduction, the highest density of precipitates of α-Al(Mn,Fe)Si phase form during heating to 450 °C in the temperature range from 350 °C to 450 °C. Quantitative particle analysis of the sheets after the whole annealing cycle indicate that the alloy deformed 96% shows the highest density of particles in the size range from 50 to 140 nm. In addition, many spherical particles up to 15 nm were observed by transmission electron microscopy, some of them were identified by electron diffraction as Al3Zr phase with L12 crystal structure.

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