Granularity-induced plastic deformation mechanism of pure polycrystalline cubic boron nitride

Abstract

Combined X-ray diffraction(XRD) profile analysis and HRTEM observation, a method for exploration of plastic deformation in pure polycrystalline cubic boron nitride (PcBN) samples with sizes of primary cBN powders was developed. XRD profile results showed that the coarse-grained PcBN exhibited a larger micro-strain ε, a greater deformation stacking faults probability fD, which was an order of magnitude larger than that of fine-grained PcBN, but a smaller twin stacking faults probability fT. It was deduced that the plastic deformation of the coarse-grained PcBN was dominated by stacking faults and mechanical twins mode, which would result in strain strengthening and then recrystallization. While the manner of growth twins was the mainly modes of fine-grained PcBN by phase transform, especially utilized the curled SP2 structure as a basis for a cubic structure nucleation. Fundamental plastic deformation principles of the ultrafine polycrystalline cBN was crucial for the field of high-precision cutting tools.