Microstructural evolution on ball-milling elemental blends of Ni, Al and Ti by Rietveld's method

The nickel-base intermetallics with Al and Ti have been extensively studied in the recent years due to their promising engineering applications specifically in the field of high temperature due to high corrosion resistance and excellent high temperature strength. The most serious negative features of such ordered intermetallics are their grain boundary brittleness. Ductility of these materials can be improved by several methods. One of them is by reducing long-range ordering or introducing disordered phases in these materials. In the present work, Ni-base ternary Ni-Ti-Al system has been prepared with an intention to produce a composite intermetallic with disordered Ni-Ti-Al alloy (ductile) and Ni-Ti and Ni-Al ordered intermetallics. After several hours of milling of constituent metal powders in a planetary ball mill, the expected phases have finally appeared in the nanocrystalline form. The structural modifications at different stages of milling have been characterized in terms of several microstructure parameters like, particle size, microstrains, stacking faults, dislocation density, etc. and quantitative estimations of individual phase have been made by employing Rietveld's powder structure refinement methodology. (C) 2002 Elsevier Science B.V. All rights reserved.