Excellent mechanical and damping properties simultaneously achieved in partially recrystallized Fe-Mn-Nb alloy

We propose a novel approach to tackle the intrinsic trade-off between the mechanical and damping properties of a cold-rolled Fe-17Mn-Nb alloy by tailoring the fraction, size and spatial distribution of recrystallized (Rexed) grains, the latter results from the initial micro-segregation of Mn during solidification because higher Mn content in the interdendritic region can promote more NbC particles dissolved for stronger retardation on Rex. An unprecedented combination of mechanical and damping properties, including ultimate tensile strength (UTS) of 920 MPa and the logarithmic decrement of vibration amplitude (δ) of 0.082 (measured at the 0.1 % strain with 1 Hz), is achieved by forming the partially Rexed microstructure consisting of retained austenite (RA) grains and ε-martensite. The austenite grains that had been reverted from the high-Mn-content region could not Rex during the annealing at 700 °C and transformed to the coarse ε blocks with the dense dislocations during cooling, contributing to the strengthening; whilst those reverted from the low-Mn-content region Rexed and then transformed to the fine ε lamellas; contributing to the damping capacity. Therefore, the different UTS-δ synergies can be realized by controlling the fraction and size of Rexed grains during the annealing to meet the specific engineering requirement.