15 research outputs found
A microtexture investigation of recrystallization during friction stir processing of as-cast NiAl bronze
As-cast NiAl bronze (NAB) was subjected to friction stir processing (FSP). Orientation imaging
microscopy (OIM) methods were used to obtain microtexture data in the stir zone (SZ) and along its
periphery. At selected SZ locations, orientation data were obtained by convergent beam electron
diffraction (CBED) methods in transmission electron microscopy (TEM). Random a phase textures were
apparent in the SZ. The a grains tended to be equiaxed, exhibited annealing twins, and were refined
to 1 to 2 mm at the edge of the SZ. The population of subgrain boundaries in a phase grains was
highest near the plate surface in contact with the tool and decreased with depth in the SZ,
reflecting deformation by the tool shoulder after the passage of the tool pin. Distinct shear
texture components were apparent in the thermomechanically affected zone (TMAZ) outside of and
along the periphery of the SZ. A texture gradient from the TMAZ into the SZ was apparent and was
steeper on the advancing side and under the SZ center than on the retreating side. The apparent
shear plane tended to align with the local interface between the SZ and TMAZ, while the shear
direction tended to align with the FSP traversing direction. In this material, the SZ–TMAZ
interface is a distinct boundary between recrystallized and deformed regions and the a-phase grain
refinement reflects dynamic recrystallization and, in locations near the SZ–TMAZ interface,
particle-stimulated nucleation (PSN) at undissolved Fe3Al particles.Defense Advanced Research Project Agency (DARPA