Jp. Chu et al., Electron backscattered diffraction study on superplastic coarse-grained Fe-27 at.%Al: processing effects, INTERMETALL, 8(9-11), 2000, pp. 1075-1079
An electron backscattered diffraction technique has been used to investigat
e detailed crystallographic features of a superplastic coarse-grained Fe-27
at.%Al alloy. Alloy samples studied have been tensile tested to failure at
800 degreesC in air under an initial strain rate of 1x10(-4) s(-1). To exa
mine processing effects, the hot isostatic pressing (HIP) has been applied
prior to the superplastic deformation. The HIPed sample shows no observable
pores in the fracture region while the sample without HIP reveals an elong
ated pore fracture structure. Nevertheless, HIP is shown to have no benefic
ial effects on the superplastic elongation, suggestive of the fact that the
alleviation of cavity formation alone is insufficient in achieving better
superplastic properties. After the superplastic deformation and the refined
grains are formed, the presence of numerous small angle subboundaries in t
he large grain interior indicates the continuous event of recovery and recr
ystallization that occurs throughout the course of superplastic deformation
. The post-deformation annealing yields a classic recrystallized large-grai
n structure, resulting from the surface-tension-induced boundary migration
that reduces the grain surface-area. Conversely, the superplastic deformati
on of Fe-27 at.%Al involves a strain-induced boundary migration that causes
the grain surface-area increase and results in a refined grain structure.
The dynamic nature of recovery and recrystallization is therefore confirmed
. (C) 2000 Elsevier Science Ltd. All rights reserved.