Room-temperature creep tests under constant load on a TRIP-aided multi-microstructure steel

This study investigated room-temperature creep tests using a low-carbon TRIP steel to clarify the TRIP effect on tensile deformation behavior under constant load. Nominal strain and strain rate increased with an increase in applied stress and those were almost stagnated at holding times of about 3.0 × 104 s. The volume fractions of deformation-induced martensite (α′) at a given true strain obtained from constant load creep tests were larger than those from tensile tests. From the in situ neutron diffraction experiments during the constant load creep tests, the phase strain of the austenite (γ) phase in the creep tests was found to be larger than that in the tensile tests at the same applied stress. This means that the phase strain or true stress of the γ phase in the TRIP steel was associated with the difference in the volume fraction of α′ between the creep and the tensile tests. The in situ neutron diffraction experiments also showed that the lattice strains of the TRIP steel in the constant load creep tests were independent of grains in γ and α phases.