This study investigates the effect of thermo-mechanical treatment on the damping capacity of the Fe-20Mn-12Cr- 3Ni-3Si alloy with deformation induced martensite transformation. Dislocation, αʹ and ε-martensite are formed, and the grain size is refined by deformation and thermo-mechanical treatment. With an increasing number cycles in the thermo-mechanical treatment, the volume fraction of ε-martensite increases and then decreases, whereas dislocation and α'-martensite increases, and the grain size is refined. In thermo-mechanical treated specimens with five cycles, more than 10 % of the volume fraction of ε-martensite and less than 3 % of the volume fraction of αʹ-martensite are attained. Damping capacity decreases by thermomechanical treatment and with an increasing number of cycles of thermo-mechanical treatment, and this result shows an opposite tendency for general metal with deformation induced martensite transformation. The damping capacity of the thermomechanical treated damping alloy with deformation induced martensite transformation greatly affect the formation of dislocation, grain refining and α'-martensite and then ε-martensite formation by thermo-mechanical treatment.

This study was carried out to investigate the effect of deformation induced martensite on the damping capacity of Fe-26Mn-4Co-2Al damping alloy. α‘ and ε-martensite were formed by cold working, and; deformation induced martensite was formed with according to the specific direction and the surface relief. With an increasing degree of cold rolling, the volume fraction of α‘-martensite increased rapidly, while the volume fraction of ε-martensite decreased after rising to a maximum value at a specific level of cold rolling. Damping capacity was increased, and then decreased with an increasing of the degree of cold rolling. Damping capacity was influenced greatly by the volume fraction of ε-martensite formed by cold working, but the effect of the volume fraction of α‘-martensite have a actually on effect on the damping capacity.

In recent years, industrial demands for superior mechanical properties of powder metallurgy steel components with low cost are rapidly growing. Sinter hardening that combines sintering and heat treatment in continuous one step is cost-effective. The cooling rate during the sinter hardening process dominates material microstructures, which finally determine the mechanical properties of the parts. This research establishes a numerical model of the relation between various cooling rates and microstructures in a sinter hardenable material. The evolution of a martensitic phase in the treated microstructure during end quench tests using various cooling media of water, oil, and air is predicted from the cooling rate, which is influenced by cooling conditions, using the finite element method simulations. The effects of the cooling condition on the microstructure of the sinter hardening material are found. The obtained limiting size of the sinter hardening part is helpful to design complicate shaped components.