Abstract: The microstructuralchangeof mechanicalalloyingof pureelemental Mg Nipowders wasin vestigated by transmission electronic microscopy ( TEM). The experimental results showed thatafter5 h milling, Mg2 Ni phase precipitated mainly from Mg grain , and no Mg2 Ni wasfound in Ni matrix. Thiscan be attributed tothe asym metricalinterdiffusion between Mg and Ni atom , which causesthecontent of Mg in Ni grain far below thestoichiometric composition of Mg2 Ni. After the growth of Mg2 Ni grain, the severe mechanical deforma tion resulting from mechanicalalloying led tothetransformation of Mg2 Ni from hexagonal tofccstructure partially, which makes Mg2 Ni grain in a composite microstructure fcc + hcp.

Key words: Mg2 Ni, mechanicalalloying, fcctransformation