Understanding thermo-mechanical processing pathways to simultaneously increase strength and damping in steels

In fluctuating load environments, the application of self-damping materials is advantageous due to their ability to reduce vibrations by dissipating heat resulting from internal lattice friction encountered by moving defects. For possible future uses in load bearing applications, this study investigates the impact of work hardening and partial recrystallization to enhance the strength of high-damping Fe-Mn based steels. A modified Granato-Lücke model is employed to describe the observed damping properties based upon the oscillation of extended dislocations. The application of pre-strain to introduce an optimal density and length combination of the partial dislocation segments, is found to increase the damping properties to over 230 % of the as received level, while simultaneously increasing the yield strength from 330 MPa to 580 MPa. A correlation is established between the damping properties and the microstructural evolution, suggesting a relation between the optimal pre-strain level and the transition between strain hardening regimes. The applicability of these findings to extended dislocation based damping properties is discussed in the context of 304 stainless steel. Furthermore, a combination of partial recrystallization with additional cold working is shown to offer an improved property combination at higher yield strengths, e.g., enhancing the damping loss tangent from tan(δ) = 0.1 to 0.021, and the uniform elongation from 6 % to 14 % for a yield strength around 920 MPa. Ultimately, the combination of partial recrystallization and additional cold working is demonstrated as a promising approach for developing high-strength, high-damping steels.