Effect of hot working variables on microstructure and properties of Fe-25AI

Abstract

The evolution of microstructures of extruded ingot Fe-25AI material during multipass hot rolling at 800°C (B2 ordered) and 1000°C (disordered) has been studied. Grain refinement was found to be difficult at 1000°C because, in the processing times, recrystallisation and grain growth were too rapid. At 800° C, however, recrystallisation and grain growth were significantly slower, which makes grain refinement and microstructural control feasible. Good agreements were found between the loads measured in rolling and the flow stress values obtainedfrom plane strain compression testing. Roll chilling was found to cause a significant increase inflow stress because the surface of the Fe-25AI material is cooled below Tc in this case. After a number of consecutive rolling passes, a dramatic increase in the flow stress was observed, which can be attributed to the additional effect of work hardening, combined with the effects of roll chilling and ordering. The properties of the material processed by different hot rolling schedules were examined by tensile testing and, by manipulation of hot rolling and heat treatment parameters, it was possible to produce higher proof stress and lower elongation, or vice versa.