ELECTRON-MICROSCOPIC OBSERVATION OF FORMA TION PROCESS OF [110]TEXTURE IN ALUMINUM -2-PERCENT IRON-POWDER METALLURGY ALLOY

In order to study formation mechanism of the preferred orientation dur ing annealing after swaging in the alloy prepared by extrusion of gas atomized powders, swaged and recovered structures as well as structure of recrystallization fronts were observed by transmission electron mi croscopies. The [110] oriented recrystallizing grains are found to ori ginate from those cells in the deformed structure that contain high de nsity Al-Fe compound particles. In the case of [110] oriented recrysta llizing grains, their {111} planes are nearly parallel to {110} planes of the both [111] and [110] oriented matrix grains, making a wedge-sh aped recrystallization front moving in the longitudinal direction. The specially oriented wedged-shaped front is free from particles, while any other recrystallization fronts are pinned down by particles either precipitating on themselves or precipitated in the recovered matrix. High resolution transmission electron micrographs suggest that the mig ration of the specially oriented interface normal to the interface pla ne proceeds by formation of {111} plane steps on the interface precede d by migration of grain boundary triple point and their following move ment in the interface plane. The formation of the preferred orientatio n has been inferred to be associated with high mobility of the recryst allization front of the [110] oriented grains in the longitudinal dire ction in relation with the special structure of the front.