Formation of supersaturated solid solutions by mechanical alloying

Results obtained from cryogenic mechanical alloying of Ni-50 at. %Al powders indicate that plastic deformation produces a nanoscale mixture of Ni and Al. This nanoscale mixture transforms to ordered NiAl phase without forming a supersaturated solid solution as the intermediate phase. The observed disappearance of the X-ray peaks of constituent elements is associated with the lower atomic scattering factor and grain refinement rather than the actual dissolution of the element. The present study also addresses the effects of thermal exposure accompanying the ball milling process. The study of Spex milling of Fe-13 at.%B-7 at.%Si demonstrates that prolonged mechanical alloying at room temperature results in partial dissolution of Si and B in Fe by enhanced diffusion. A supersaturated solid solution of 4 at.% B in Fe is observed.