Study on the effect of milling parameters on HE-MA nanostructured Al-Graphene cermet particles

Abstract

Nanocrystalline grains have proven to be excellent reinforcing elements in nanostructured particulate materials. On the other hand, carbon allotropes, especially graphene and carbon nanotube (CNT), exhibit elastic modulus in the range of 1 TPa (theoretical) and tensile strength in multiple orders greater than that of steel. This study aims at synthesizing high-strength nanostructured ceramic-metallic (cermet) particle feedstock in a high-energy mechanical alloying (HE-MA) process based on an Al-graphene composite comprehensive design-of-experiments (DoE). The goal is to optimize milling process parameters, including milling time, batch composition, ball-to-power (BPR) ratio, and milling agent, for the particles to be eventually fed into a high-pressure cold spray coatings development. The milled powders are characterized using SEM, EDS, XRD, and laser particle diffractometer to study the morphology and microstructure, elemental composition, grain size and crystal orientation, and particle size distribution (PSD), respectively. Results show it was possible to attain required structure and PSD at a 10:1 BPR with 5-mm diameter ball, at 1200 rpm, and 4 h of milling.