Effect of milling methods on microstructures and mechanical properties of A16061-CNT composite fabricated by spark plasma sintering

In this paper the effect of CNTs additive and different milling techniques on the microstructure and mechanical properties of the A16061-CNTs metal matrix composites was studied. Planetary and horizontal attritor milling with different modes were used as milling techniques. The levels of damage introduced to the surface of multi walls carbon nanotubes (MWCNTs) were characterized through analyzing the Raman peak ratio (I-D/I-G) characteristic of each processed sample. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the morphology of the Al-6061alloys and Al-6061-MWCNTs composite powders. X-ray diffraction (XRD) was used for phase identification and the mechanical properties of the composites were determined by means of tensile tests. Despite the level of energy imposed on the powders, among the three used milling modes, the two-stage milling mode including low speed (200 rpm) followed by high speed (1000 rpm) horizontal milling was the most effective in dispersing of CNT, since no clusters were found. Accordingly, the slight addition of CNT (1.5 wt%) could elevate the tensile strength from 265 to 538 MPa, with respect to un-reinforced alloys processed in the same conditions.