Thermal and X-ray analyses of aluminum–titanium nanocomposite powder

Abstract

The present study has investigated the complex mechanisms in the aluminum–titanium system with different percentages of titanium through a combination of thermal and X-ray analyses. Thermogravimetry, derivative thermogravimetric, X-ray diffraction, scanning electron microscope and transition electron microscope were used for characterization of the samples. Initially, different Al–Ti powder mixtures were produced by high-energy ball milling and after 30 h of milling the phases generated at different percentages of Ti were analyzed. The XRD results revealed that the intermetallic Al3Ti powder is obtained after a certain duration of milling. In addition, L12 to D023 phase transformation is possible with increase of the Ti percent. Analyses of the powder annealed at different temperatures yielded interesting results, including the effect of stearic acid as the surface control agent on phase transformations of the aluminum–titanium system and also the formation of unexpected phases such as Al4C3 and TiC. Moreover, ductile to brittle transition during phase transformations of the intermetallic Al3Ti powder was quite conspicuous, which could result in more homogeneity of the powders and the occurrence of more reactions in the system. For example, formation of D023-Al3Ti powder which is more brittle compared to L12 resulted in the exit of Al from among its layers, leading to the increase of the chances for Al reaction with the system impurities.