Effect of homogenisation treatment on precipitation, recrystallisation and properties of Al – 3% Mg – TM alloys (TM = Mn, Cr, Zr)

• Coherent Mn-bearing particles are found after homogenisation annealing.
• Cr dissolved in the Mn-bearing phase as shown by point TEM-EDS analysis.
• The activation parameters of relaxation effects are estimated.
• Superplasticity is achieved after treatment with high temperature homogenisation.

The influence of homogenisation regimes on precipitations of fine Mn-bearing dispersoids, recrystallisation kinetics, grain structure, mechanical properties and superplasticity of cold worked sheets of Al-3Mg alloys with Mn, Cr and Zr is studied. Precipitates of coherent compact and plate-like particles of Mn-bearing phase are found after homogenisation annealing. Activation parameters of the low-temperature internal friction, internal friction solute grain boundaries peak and dislocation nature thermally activated relaxation peak in the samples treated by different regimes are compared. High-temperature homogenisation at 460 °C provides a higher volume fraction and finer particles of Mn-containing phases after thermomechanical processing compared to low temperature treatment at 380 °C. Consequently, finer grains and higher superplasticity indicators are achieved in a recrystallised state. Polygonisation is observed during heating of the cold worked samples pre-homogenised at 380 °C: recrystallisation temperature is increased and mechanical strength at room temperature is improved.

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