Effect of Al content on thermophysical properties in Fe–17Mn–0.7C twinning-induced plasticity steel

The present study investigated the effect of Al addition in Fe–Mn–C twinning-induced plasticity (TWIP) steel on thermophysical properties with temperature using the three TWIP steels with different Al contents. The average thermal expansion coefficient (β) of the TWIP steels was approximately 23 × 10⁻⁶ °C⁻¹, which is higher than those of plain carbon and austenitic stainless steels. The density (ρ) of TWIP steel decreased with the addition of Al content regardless of temperature due to the low density of Al compared with Fe. The thermal diffusivity (α) and thermal conductivity (k) decreased with the addition of Al content in TWIP steels because the thermal resistivity increased with the addition of alloys in metals. The solute Al atom caused the lattice distortion and increased the opportunity of electron and phonon scattering, resulting in increase in yield strength and decrease in α and k. The k of TWIP steels linearly increased with temperature and it was significantly low compared with that of plain carbon steels. For example, the k value of plain carbon steels was approximately 45 W/m °C at 100 °C, whereas that of TWIP steels was approximately 14 W/m °C at 100 °C. Meanwhile, the k of TWIP steels and plain carbon steels exhibited the similar value of 28 W/m °C at 1000 °C. Great care must be taken on thermal stress in products when manufacturing TWIP steel products through welding, heat treatment, hot working, etc. owing to the high β and low k in TWIP steels.