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

The effects of temperature on the amorphization of Zr-Al solid solutions have been investigated by ball milling Zr100-xAlx powder blends at different temperatures. At low milling temperatures, the Zr-Al solid solutions amorphized under the polymorphic constraint imposed by intensive external forcing. At elevated temperatures, the solid solution and the amorphous phases coexisted in an obvious two-phase region, signaling a transition approaching two-phase metastable equilibrium. The Al concentration needed for the complete amorphization of Zr-Al increased with increasing milling temperature. These observations, and in particular, the apparent reentrant liquidus, can be explained in terms of the temperature dependence of the external forcing effects brought in by the nonequilibrium milling process in this dynamic driven system. (C) 1999 American Institute of Physics. [S0021-8979(99)07609-4].