Two-step processing of hydrogen storage FeTi Alloys: influence on reaction temperature

In the present work, nanostructured FeTi powders were produced by mechanical alloying, avoiding the unfavorable agglomeration problem by using a low energy milling (e.g. 300 rpm) of pure metallic constituents, Fe and Ti, followed by subsequent heat treatment at 800ºC. A major achievement of this research was to show that by modulating the milling intensity and total milling time, the high temperature synthesis reaction of FeTi (1100ºC) can be partially or totally suppressed, reverting instead to a metastable reaction path at low temperature (650ºC). The mechanical “activation” modifies the reactivity of the system, producing a very thin Ti /Fe layers. That in conjunction with a high level of defects induced mechanically may be responsible for the metastability