The compositions of carbide particles which precipitate during the isothermal transformation of a low-alloy steel containing both V and Ti have been investigated by atom-probe field-ion microscopy. The carbides were found to have a mixed (V, Ti)C composition and, following their initial precipitation, contained a small quantity of Fe. This disappeared on subsequent long-term ageing. Analysis of relatively large particles produced by long-term ageing showed them to have the approximate chemical formula (V0·45Tio·55)Co·84. It is suggested that this may be the composition of an ordered compound, having an increased binding energy, which previous evidence suggests to exist.
