Dynamic precipitation behavior before dynamic recrystallization in a Mg-Zn-Mn alloy during hot compression

Abstract

The dynamic precipitation behavior before dynamic recrystallization (DRX) in a ZM51 alloy during hot compression at strain rate from 1 s−1 to 20 s−1 was investigated by transmission electron microscope (TEM) and small-angle X-ray scattering (SAXS) technique. The DRX critical strain decreases with increasing the strain rate. With the same deformation temperature and the identical strain, (0001)α plates (β′2) are dominant in the matrix at the strain rate of 1 s−1, while [0001]α rods (β′1) and spherical precipitates (β′2) occur at the higher strain rate (έ ≥ 10 s−1). At the higher strain rate, the total volume fraction of precipitates decreases initially and then increases, with the maximum value of 3.41%. The average length of β′1 rods decreases from (27 ± 11) nm to (20 ± 5) nm, and the mean rod diameter decreases from (16 ± 5) nm to (10 ± 3) nm. While the average thickness and mean diameter of β′2 plates decrease to (10 ± 2) nm and (15 ± 5) nm, respectively, and the spherical β′2 radius decreases from (15 ± 2) nm to (12 ± 3) nm. When deformed at 300 °C with a strain rate of 10 s−1, the alloy is featured with three types of precipitates with the strain of 0.05, indicating that the evolution regularities of dynamic precipitates during the high strain rate deformation is different from that in the static aging process.