Development of a high wear resistance aluminium matrix nanoreinforced composite

Abstract

aBecause of the present economic conditions, the great energetic dependence on petroleum derivatives and the restrictive regulations of environmental pollution, development of new materials and processing methods has become a very important technological challenge. 7075 aluminium alloys (Al-Mg-Zn-Cu) have been widely used as structural materials in the aeronautics industry because of their attractive properties such as very low density and high specific strength, ductility, toughness and resistance to fatigue. In the last few years many studies have been carried out to enhance these properties by developing aluminium matrix microparticulate reinforced composites. These properties can be improved by the use of nanoparticulate reinforcements. In this work, some steps of the fabrication of a new advanced aluminium matrix nanoreinforced composite are analyzed. A powder metallurgy 7075 aluminium alloy was chosen as the matrix and TiC nanoparticles were used as reinforcement material. Although the manufacturing process consists of many stages (mechanical alloying, sintering, extrusion, aging treatment, etc.), in this work only mechanical alloying and sintering are considered. Microstructural characterization of samples was carried out by means of optical microscopy and SEM techniques. Transmission electron microscopy was used to determine the adequate distribution of the reinforcement material. Vickers hardness tests were carried out and structural changes were studied by X-ray diffraction tests.

Effect of Carbon Nanotube Content and Mechanical Milling Conditions on the Manufacture of AA7075/MWCNT Composites

“…To optimize the dispersion of MWCNTs in composite powders, three mechanical ball milling strategies were compared in this study. These were carried out by following a cyclic operation mode in which the rotation speed was varied over 1 min cycles, maintaining the higher speed indicated in first place for 48 s and the second lower speed for the last 12 s. Previous research [33] showed that cyclic operation improves the efficiency of the process by avoiding the agglomeration and sticking of particles and reducing the milling time required to obtain a smaller-grained structure compared with conventional milling.…”

MWCNT-Reinforced AA7075 Composites: Effect of Reinforcement Percentage on Mechanical Properties

“…As a process controlling agent (PCA), amide micro-wax (0.5% by weight) (Licowax ® C micro powder, Clariant, Muttenz, Switzerland) was used to avoid cold welding between the powder particles, limiting agglomeration, and to prevent detrimental welding of the powder to the balls, the container walls and blades of the mill. A cyclic operation mode was performed for mixing AA7075 powders and the MWCNTs, alternating the rotary speed between 1300 (48 s) and 1000 rpm (12 s) in cycles of 1 min for 4 h. The cycle operation procedure has been proven to avoid sticking and agglomeration [26] and, compared to constant operation, has a significant influence on particle size reduction [27]. To study the variation of size and morphology of the composite powders and verify the dispersion of the nanotubes with time, samples were extracted after 2 and 4 h of HEBM.…”