SOLID-STATE REACTION IN Al-Fe BINARY SYSTEM INDUCED BY MECHANICAL ALLOYING

Abstract

Mechanical alloying (MA) is a solid-state powder processing method which has the ability to synthesize a variety of new alloy phases including supersaturated solid solutions, nanocrystalline structures, amorphous phases and intermetallic compounds. In this investigation, the interaction between aluminum and iron caused by MA of Fe-XAl (where X ranged between 30 to 90%) has studied as a function of milling time post heat-treating temperatures. The sequences of structural and/or phase transformation and the behavior of mechanically alloyed powders have been assessed using XRD, hardness and magnetometer. It was found that, during mechanical milling of element powder Al and Fe, five milling stages can be categorized, namely, particle flattening, welding predominance, equiaxed formation, random welding orientation and steady state composite particles. All milled powders showed nano-sized powder mixtures after milling for 20hrs. When Fe-30Al powder was milled for 150hrs, partially ordered AlFe phase was obtained. However, when these saturated solid solutions were heat treated at 5000C, AlFe intermetallic was precipitated in fully ordered. When the Al increasing up to 40% and milled for 50hrs, the XRD pattern showed a broad halo, for solvent spectrum which mst formation of an amorphous phase. When Fe-60%Al powder mixture was mechanically milled Al5Fe2 intermetallic formed associated with an amorphous phase, which transformed into Al3Fe intermetallic by heat treating at5000C.In case Fe-75%Al an Fe-90%Al milled for 150hrs only Al peaks abroad and were shifted to higher angles, suggesting that Fe atoms diffused into Al, leading to the formation of a solid solution.