Nanostructured powder for nano-B₄C particulate-reinforced aluminium–matrix composite prepared via cryomilling

Abstract

Nanostructured powders for aluminium-based composite reinforced with nanometric B₄C particles were synthesised by cryomilling. The morphology evolution of Al/B₄C powder during cryomilling was observed by scanning electron microscopy. The microstructure of the composite powder, the dispersion of B₄C particles in aluminium matrix, as well as the quality of Al/B₄C interface after cryomilling were investigated using transmission electron microscopy and high-resolution transmission electron microscopy, respectively. Results revealed that morphology evolution could be attributed not only to the coupled effects of the plastic deformation, severe comminution and cold welding of the composite powder during cryomilling, but also to the ‘bridge-making’ mechanism of the nanometric B₄C particles immersed in the liquid nitrogen. The average size of aluminium grains in the composite powder milled for 2 hours was measured as 100–200 nm. Furthermore, the homogeneous distribution of the nanometric B₄C in aluminium and the clean metallurgical Al/B₄C interfaces were also achieved within the composite powders prepared in this work.

Keywords:

• Nanocrystalline
• Boron carbide
• Aluminium–matrix composite
• Cryomilling
• Microstructures