Effects of heat treatment on microstructure and mechanical properties of extruded AZ80 magnesium alloy

• Discontinuous precipitation grew into the grains from grain boundaries with a lamellar growth.
• Continuous precipitation formed in the remaining areas within the grains unoccupied by DP.
• The interfaces between discontinuous precipitation and continuous precipitation areas were clear.

Microstructure evolution of the extruded AZ80 magnesium alloy and different precipitation behavior of β-Mg17Al12 phase in different heat treatment conditions were investigated. Solution treatment caused the dissolution of β-Mg17Al12 phase and the grain coarsening. During aging, discontinuous precipitates were preferentially initiated at some of the grain boundaries and then continuous precipitates appeared in the grain interiors. In the period of direct-aging, discontinuous precipitates formed between the banded structure and no continuous precipitate appeared. After solution and aging treatment, an improved combination of strength and elongation was obtained. The highest strength was achieved for the extruded AZ80 sample after directing-aging treatment.

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