The Effect of Iron Content on the Primary Recrystallisation of Dilute Aluminium-Iron Alloys.

The influence of iron content on the recrystallisation behaviour of Al-rich, Al-Fe alloys has been studied after both isochronal and isothermal annealing, following cold-rolling reductions of 60%. A preliminary investigation of the suitability of several techniques, which are conventionally used to study re crystallisation, showed hardness testing and quantitative metallography to be the most accurate and easily applied techniques. It has been shown that increasing the Fe content in solid-solution alloys raises the temperature at which the recrystallisation process starts, and retards its progress, whereas the reverse occurs in the case of two phase alloys. Care has been taken to standardise the solid-solution content of the matrix within the two phase alloys and a separate series of control experiments has shown that variations of the size of FeAl[3] particles (within the range encountered here) do not affect the re crystallisation behaviour at a fixed composition, However, Increasing the grain size at a fixed composition has been shown to retard the recrystallisation process, to an extent which decreases as the FeAl[3] particle content increases. This has enabled a re-interpretation of the results in terms of behaviour at constant grain size, which shows that increasing the Fe content (in two phase alloys) has no effect on the temperature at which recrystallisation starts, although its progress is accelerated. Finally, the acceleration of recrystallisation was shown to be associated with an increase in the nucleation rate as the FeAl[3] concentration increased. The results have, therefore, been interpreted in terms of the competing influences of grain boundaries and FeAl[3] particles as possible nucleation sites, and a model, which is consistent with previous work, has been proposed