Application of ball milling in the synthesis of AA 7075–ZrO2 metal matrix nanocomposite

• Effect of two different media on average particle size of ZrO2 was found.
• Times higher than 80 h did not produce significant ZrO2 particle size reduction.
• Destabilization of initial ZrO2 structure during milling.
• Fifteen hours of milling time was required for obtaining a complete dispersion of ZrO2.

Ball milling was used to reduce the particle size of yttria-stabilized ZrO2 powders with the aim of introducing it into the AA 7075 matrix. It was observed that during the mechanical milling of the ZrO2 powders a destabilization of the tetragonal structure occurred, which was confirmed by the X-ray diffraction results. A transition from tetragonal to monoclinic structure resulted as a consequence of the application of ball milling. The synthesis of the composite was carried out in the same way by applying mechanical ball milling in order to disperse 2 and 5 wt.% of zirconium oxide particles into the Al alloy matrix. It was found that longer times were needed for the 5 wt.% of ZrO2 to achieve a complete dispersion into the matrix, unlike 2 wt.% of ZrO2 sample, being 15 and 10 h, respectively. It was evident that the presence of ZrO2 particles had a marked influence upon the powder morphology and particle size of the matrix during the milling process. Despite the structural change observed, a relatively good homogenous dispersion of ZrO2 particles was found after ball milling.

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