Microstructural evolution and precipitate behavior of an AZ61 alloy plate processed with ECAP and electropulsing treatment

Abstract

Electropulsing treatment processing (EPT)-induced microstructural evolution and precipitation behaviour of the β-Mg17Al12 phase in the AZ61 alloy were investigated by using scanning electron microscopy, X-ray diffraction and electron backscattering diffraction patterns. The results revealed that the EPT method is efficient in achieving a near-spherical Mg17Al12 phase (approximately 300 nm) and uniform ultrafine-grained structure (approximately 900 nm) featuring a weakened texture in AZ61 alloy plates after EPT for 40 μs-3 min. The improved structural characteristics are attributed to the rapid recrystallization and grain refinement induced by EPT at lower temperatures and in a short time. On this basis, kinetics analysis of the spheroidization and the dissolution of the β-Mg17Al12 precipitation phase and grain refinement and growth in the samples after EPT were performed. Furthermore, the mechanism of precipitation phase transformation and grain refinement during EPT was discussed.