Microstructural evolution during mechanical milling of pre-alloyed TiAl powders

Abstract

Microstructural evolution during mechanical milling of pre-alloyed gamma-(Ti52Al48)(95)B-5 powders was investigated. It has been shown that the initial gamma phase in the as-melt-extracted alloy becomes disordered by mechanical milling. In addition, an amorphous phase is formed with the same composition as the disordered gamma phase. The disordered gamma and amorphous phases eventually transform to a nanocrystalline Ti-Al hcp solid solution after the completion of milling. Comparison of the present result with the previous results on mechanical milling of elemental Ti and Al powders indicates that the final phase formed by mechanical milling does not originate from the initial structure. Rather, the nature of the final phase depends on the relative stabilities of various phases, modified by the deformation induced by mechanical milling.