On coherent carbonitride precipitation in commercial microalloyed steels

Fine vanadium carbonitride particles nucleated during interphase precipitation have been investigated in the transmission electron microscope under controlled conditions of diffraction contrast. On dark-field micrographs taken with a carbonitride reflection, particle sizes ranged from 5 nm down to below 2 nm in diameter. No matrix strain around these particles could be detected when matrix reflections were used to produce diffraction contrast under two-beam conditions. It was concluded that the vanadium carbonitrides had precipitated in the form of incoherent particles.