Influence of Long-Ordering Parameter and Boron Microalloying on Mechanical Properties of Nanocrystalline Intermetallic Compound Ni_3Al

摘要

The influence of boron on the thermal stability and mechanical behaviour of nano- and submicrocrystalline Ni_3Al intermetallic compounds was investigated by comparing a high-purity material with a boron-doped (0.1 wt%) compound. The nanocrystalline structure was obtained by high pressure torsion (HPT) on a Bridgman anvil-type unit. It was shown that due to HPT the entirely disordered structure with a grain size of 20 nm was formed in the material. The non-monotonic dependence of mechanical properties (at 20 °C) on temperature of annealing was revealed. The material in an entirely disordered nanocrystalline state has the maximum strength and ductility. Partial formation of the long-range ordering parameter in the range of nano- and submicrocrystalline grain size correlates with the loss of ductility and decrease in strength. Growth in ductility and strength is observed with increasing grain size. The influence of a grain size and long-range ordering parameter on mechanical properties is evidently connected with specific features of plastic deformation and failure processes.