In situ formation of FeAl–Al2O3 nanocomposite at different conditions of milling and subsequent annealing

Abstract

FeAl–Al2O3 nanocomposite powder was synthesised under different conditions of milling and annealing. The structure, morphology and microstructure of the milled powders were monitored by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. Results showed that the formation of FeAl and Al2O3 took place in explosive mode during milling with the cup speed of 600 rev min−1. However, at the cup speed of 500 rev min−1, FeAl and Al2O3 were synthesised only during annealing. Formation of the FeAl and Al2O3 was completed after 120, 270 and 360 min of milling at the ball to powder weight ratios (BPRs) of 5∶1, 15∶1 and 10∶1 respectively. Maximum microhardness of 8·8 GPa was obtained in the 270 min milled sample with the BPR of 15∶1 and cup speed of 600 rev min−1. Mean grain size of 30 nm was calculated in the annealed FeAl that was in consistent with TEM results.