Thermal evolution of high-purity and boron-doped sub-microcrystalline Ni3Al produced by severe plastic deformation

The influence of boron on the structural stability of sub-microcrystalline Ni3Al intermetallic compounds was investigated by comparing a high-purity m aterial with a boron-doped (0.1 wt%) compound. The nanocrystalline structur e was obtained by severe shear deformation under quasi-hydrostatic pressure . Residual electrical resistivity, Vickers microhardness, X-ray diffraction and transmission electron microscopy were used to characterize the materia l evolution during thermal treatments in the temperature range 293-1313 K. After severe deformation the materials were disordered, with a small crysta llite size of about 20 nm, similar in both materials. During isochronal ann eals, the evolution of the microstructure, the long-range ordering and the recovery of the investigated properties took place at higher temperatures i n the boron-doped compound, i.e. the thermal stability of the cold-worked s tructure was higher. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.