A study on the preparation of iron aluminium based intermetallic alloy by aluminothermic smelting technique

Iron aluminium based intermetallic alloys or iron aluminide alloys are usually made by conventional melting and powder processing routes. Melting is carried out either in vacuum induction melting or are melting furnaces. However,the use of high vacuum and high temperature expensive furnaces, high cost associated with the procurement of pure individual metal components, operational problems during melting stages are some of the most deterrent factors in making these alloys by melting route. Powder processing route utilises atomised, carbonyl or rapidly solidified pre alloyed powders as starting materials and alloying is carried out either by mechanical alloying or reaction synthesis or by consolidation through hot isostatic pressing. This process also involves many processing steps and considerable expense. In the present investigation, it has been found possible to eliminate the above problems by adopting a simple aluminothermic reduction (thermit) smelting technique for the preparation of iron aluminide alloy of targetted composition Fe-16A1-5.46Cr-0.5V-0.05C (wt %) by the direct co-reduction of oxides of iron,chromium and vanadium in presence of carbon and excess aluminium. Incorporation of slag fluidizer CaO amounting to 10 wt % of total charge, aluminium, 10 wt % excess over stoichiometric requirement and carbon, double the theoretical amount have been found to be adequate to form the above alloy with maximum overall yield of 99.4 wt %. The compositional variation of alloying components Like iron, chromium,vanadium, aluminium and carbon in the aluminothermically produced iron aluminide alloy from the target composition have been minimized under optimum experimental conditions. The reactions have been found to be well controlled, rapid and self-sustaining and are conducted in an off-furnace manner using a simple experimental set-up. Studies on composition and microstructure characterization, hot rolling behaviour and oxidation resistance of the said alloy points towards its suitability for use. (C) 1998 Elsevier Science S.A. All rights reserved.