The effect of type of atmospheric gas on milling behavior of nanostructured Ti6Al4V alloy

Recently fabrication of titanium alloys through solid state processes such as mechanical alloying has been greatly taken into consideration. In the present investigation the effects of common atmospheric impurities, oxygen and nitrogen, on the fabrication procedure and milling behavior of nanostructured Ti–6Al–4V alloy during mechanical alloying (MA) was studied. In this regards, elemental powders were milled under three different protective atmospheres of air, 90% and 99.998% pure Argon. Results indicated that, samples milled under Ar with 90% purity featured the best behavior and reached a nanostructure and subsequent amorphous state in shorter time periods. This was considered to be due to Ti lattice distortion made by interstitial element such as O2 and N2.

The present investigation has been based on evaluation of the effects of different milling atmospheres on production of nanocrystalline Ti6Al4V powder from elemental powders by means of high energy mechanical milling. The structural and morphological changes of powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM).Figure optionsDownload as PowerPoint slideHighlights
► The type of protective gas and its purity defines the results of mechanical milling.
► A percentage of O2 and N2 in protective gas improve the alloying procedure.
► Increasing the amount of O2 and N2 up to 9% accelerates amorphous phase formation.
► In Ti alloys containing V, the percentage of O2 and N2 must be accurately measured.
► Ti6Al4V powder is extremely prone to oxidation during milling in the air.