Amorphization of Zr-Al solid solutions under mechanical alloying at different temperatures

The effects of temperature on the amorphization of Zr-Al solid solutions ha ve been investigated by ball milling Zr100-xAlx powder blends at different temperatures. At low milling temperatures, the Zr-Al solid solutions amorph ized under the polymorphic constraint imposed by intensive external forcing . At elevated temperatures, the solid solution and the amorphous phases coe xisted in an obvious two-phase region, signaling a transition approaching t wo-phase metastable equilibrium. The Al concentration needed for the comple te amorphization of Zr-Al increased with increasing milling temperature. Th ese observations, and in particular, the apparent reentrant liquidus, can b e explained in terms of the temperature dependence of the external forcing effects brought in by the nonequilibrium milling process in this dynamic dr iven system. (C) 1999 American Institute of Physics. [S0021-8979(99)07609-4 ].