Microstructure Characteristics of MWCNTs/AZ80 Composites at High Temperatures

The volume fraction of 3.1% MWCNTs/AZ80 composites were prepared using the friction stir processing technique. The microstructure and phase of composites at different thermal exposure temperatures for 3 hours were analyzed by optical microscopy and XRD tests. The results show that the MWCNTs/AZ80 composites prepared by FSP are fine grains, and the microstructures are equal axial grains after dynamic recrystallization. After FSP processing, the content of β-Mg₁₇Al₁₂ precipitates in the T6 state of AZ80 magnesium alloy is reduced. With the addition of MWCNTs, the grains of MWCNTs/AZ80 composites are finer and the content of β-Mg₁₇Al₁₂ is smaller. With the increasing of thermal exposure temperature, the microstructure of the composite becomes coarse, and the content of β-Mg₁₇Al₁₂ precipitates in the composite is increased. However, the content of β-Mg₁₇Al₁₂ precipitates of composites is decreased when the thermal exposure temperature is higher than 150 ℃.