Dynamic recrystallization in Al single crystals revealed by rapid X-ray Laue method

An experimental study on the microstructure development and stress–strain behavior during high temperature deformation of aluminum single crystals was made by the use of an in-situ X-ray technique. The main purpose of this experiment was to detect the dynamically recrystallized grains during deformation. The specimens for the compressive test (3×3×6 mm3) were prepared from high purity (five nine grade) Al single crystal ingots. Compressive deformation was made at 373–473 K with initial strain rate 10−4–10−3 s−1 using a test machine designed so as to fit on the camera stage of the X-ray apparatus. The 〈111〉 crystallographic orientation was chosen as the compression axis. Transmission Laue diffraction patterns was recorded during deformation. The utilization of imaging plates, Fuji ST-VA, instead of conventional photographic emulsion films, enabled to reduce the exposure time down to <2 s for the X-ray radiation generated from a normal focus W-tube operated at 1.4 kW. The deformed specimens were subjected to optical microscopy. For all the deformation conditions employed in the present work, a large stress fall was observed after the first stress peak. At 473 K, the strain corresponding to the first stress peak was around 0.15 and tended to increase with decreasing strain rate. X-ray Laue spots began to streak as strain increased, and new spots without streak appeared at around or just after the first stress peak, indicating that new fresh grains had been dynamically formed. These results are in consistent with those of the previous workers. Mechanisms of dynamic recrystallization in single crystals were discussed.