A one-step heat treatment comprising isothermal holding in the two-phase region for different time periods and subsequent quenching contributed to the development of a ferrite and martensite dual-phase structure in TiMo microalloyed steels with different carbon and microalloying element contents. Irrespective of the Ti/Mo atomic ratio, a dual precipitate morphology, namely interphase precipitation and random precipitation, was found in the ferrite matrix. Furthermore, under the fixed carbon content, harder ferrite grains were obtained in the steel with a high Ti/Mo atomic ratio. This could be explained by the fact that a large volume fraction of tiny-sized carbides formed within the ferrite matrix when the Ti/Mo atomic ratio was increased. In addition, several microalloyed steels with different Ti/Mo atomic ratios listed in highly-cited patents were also retrieved and analyzed to support the above deduction. Display omitted •A one-step heat treatment comprising isothermal holding in the two-phase region and quenching was performed in the specimens.•A high theoretical volume fraction of precipitated carbides was obtained in the steel with a high Ti/Mo atomic ratio.•In comparison to Ti/Mo, the Ti + Mo/C atomic ratio is not related to the strengthening of ferrite grains.•Irrespective of the Ti/Mo atomic ratio, dual precipitation morphologies can form simultaneously in the same ferrite matrix.•A new distinguished carbide, the V-shaped carbide, can be found in some ferrite grains after long time isothermal holding.