Phase changes in Fe72−x Al28Cr x (x = 0,2,4,6) alloys due to mechanical strain
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Fe72−x Al28Cr x (x = 0,2,4,6) are made by arc melting a mixture of constituent elements in stoichiometric proportion, in argon atmosphere. The ingots so obtained are filed to make powder samples thereby giving them substantial mechanical deformation. It is observed that as-powdered samples show hyperfine field distribution typical of α-phase, where the atoms are randomly distributed on the available sites. Annealing at 900°C for 60 h leads to preferential occupation of lattice sites by the atoms and this results in better defined groups of hyperfine magnetic field (HMF) which can be associated with specific configuration in the neighbourhood of probe iron atoms. The average HMF is found to decrease sharply with increasing Cr concentration even though the net chromium concentration remains low (≤6 at%). The results show that cold working on samples is very important in changing the atomic ordering and must be taken into account if properties of equilibrium phases are probed.
KeywordsIron aluminides Mössbauer spectroscopy phase transformation mechanically driven transformation
PACS Nos76.80 61.72.J 78.70.B 81.40.E
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