The production of ultra fine grained Al-SiCp composites produced via high energy ball milling

Aluminum-copper alloy EN AW 2017 (Al-3.9Cu-0.6% Mn-0.7%Mg) based composite powders reinforced with 5 and 15 vol. % SiC particulates were produced by high energy ball milling(HEM) process. The milling times range between 10 min and 6 h. After milling for a certain time, i.e., 2 h, the cellular structure of CuAl2 intermetallic particles initially present in the matrix and precipitate at the grain boundaries that were destroyed and distributed along the deformation axis. XRD results clearly showed that the X-ray diffraction peaks of CuAl2 disappear after 2 h milling time suggesting that the submicrometer sized intermetallic CuAl2 particles dissolved into the aluminum matrix. This was also confirmed by SEM investigation. During subsequent milling of composite blends (2 h and more) the reinforcement particles were heavily fragmented. Thus they exhibited a significant reduction in size. The results indicate that the particle size of SiC and CuAl2 was refined greatly after 6 h of high energy ball milling. However, it is clear that the particle size distribution even after the longest period of milling, 6 h, showed no significant narrowing. The crystallite size of the composites was reduced to below 45 nm which was confirmed by X-ray line broadening analysis