Thermal Stability of Cryomilled Al-Mg-Er Powders

الملخص EN

In this study, the thermal stability of nanostructured Al-Mg alloy powders was investigated.

Two alloy compositions, Al-5Mg-0.1Er and Al-5Mg-0.5Er (wt.%), were cryogenically milled for 30 h to produce nanostructured powders.

The microstructure of the milled powders with increasing temperature was investigated by differential scanning calorimetry (DSC) with one-hour annealing performed at selected temperatures followed by X-ray diffraction (XRD) and electron microscopy analysis.

Prolonged milling led to significant oxygen pick-up in the powders.

The Al-5Mg-0.1Er powders experienced grain growth typical of cryomilled Al-Mg powders, while the Al-5Mg-0.5Er alloy showed improved thermal stability.

An average grain size of ~20 nm was observed up to 400°C (~0.8Tm) in the Al-5Mg-0.5Er powders, and abnormal growth at 550°C resulted in a maximum observed grain size of 234 nm.

Thermal stability in the Al-Mg-Er powders is attributed to the combined effects of solute/impurity drag and second-phase pinning (nanoscale oxides, nitrides, and oxynitrides) that impede grain boundary motion.