We have developed a new class of ferritic steels strengthened by hierarchical precipitates (HPs) of Ni2TiAl/NiAl or a single precipitate (SP) Ni2TiAl for applications as steam-turbine materials. These HPs or SP-ferritic steels exhibit significant improvement of the creep resistance at 973 K in terms of the steady state creep rate and creep rupture time. In particular, the HPs-alloy shows superior creep resistance to the SP-alloy. This trend implies the considerable strengthening arising from the L21 precipitate and the HPs structure. The objective of the proposed research is to use the neutron source using Engin-X at ISIS to observe the lattice-misfit, elastic-strain evolution and load transfer between the precipitate(s) and Fe-matrix during in-situ creep and tension at elevated temperatures, which will provide in-depth understanding of the effect of the HP on the creep behaviors.