X-ray diffraction peak from minor phase in mechanically alloyed Al-Ti

Abstract

Refining of Ti powder particles and their dissolution into the Al matrix during mechanical alloying (MA) were investigated by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) as functions of alloy composition, milling time and ban to powder ratio (BPR). It is found that Ti particles less than 20 nm are observed in a dark field image of mechanically alloyed Al-10 mass%Ti whose XRD pattern exhibits no Ti peak. The observed change of lattice constant of AI indicates that about I mass%Ti can be solved in Al after MA for a long time, independent of alloy composition, milling time and BPR, suggesting that most of Ti particles are retained in the Al matrix. It is concluded that the disappearance of XRD peaks in mechanically alloyed Al-10 mass%Ti is not simply attributable to the dissolution of the Ti into Al, but is associated mainly with extreme refining and/or heavy straining of Ti particles.