Microstructure and mechanical properties of differently extruded AZ31 magnesium alloy

Profiles of the magnesium alloy AZ31 were produced by conventional indirect extrusion and by indirect extrusion into counterpressure with variations of the billet temperature T-B from 200 degrees C up to 350 degrees C. Microstructural examination by optical microscopy showed that for extrusion trials carried out with billet temperatures T-B <= 250 degrees C fine dynamically recrystallized grains are found while elongated grains of the former cast structure remain. Above T-B >= 300 degrees C most grains show higher dynamic recrystallization kinetics and additional static recrystallization and increase to grain sizes of d = 30-50 mu m. At T-B <= 250 degrees C the typical extrusion < 10 (1) over bar0 > fiber texture is found, at T-B >= 300 degrees C a < 10 (1) over bar0 >/< 11 (2) over bar0 > double fiber texture is formed due to static recrystallization. The results of the quasistatic mechanical tests are due to these differences in the microstructure.