THERMAL EVOLUTION OF HIGH-PURITY AND BORON- DOPED SUB-MICROCRYSTALLINE Ni_3Al PRODUCED BY SEVERE PLASTIC DEFORMATION

摘要

The influence of boron on the structural stability of sub-microcrystalline Ni_3Al intermetallic compounds was investigated by comparing a high-purity material with a boron-doped (0.1 wt) com- pound. The nanocrystalline structure 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 material evolution during thermal treatments in the temperature range 293-1313 K. After severe deformation the materials were disordered, with a small crystallite size of about 20 nm, similar in both materials. During isochronal anneals, the evolution of the microstructure, the long-range ordering and the recovery of the investigated properties took place at higher temperatures in the boron-doped compound, i.e. the thermal stability of the cold-worked structure was higher.