Heating rate effect on liquid Zn-assisted embrittlement of high Mn austenitic steel

The effect of heating rate on liquid metal embrittlement (LME) of a galvanized twinning induced plasticity (TWIP) steel was investigated by hot tensile testing. The specimens were heated with different heating rates to 600, 700 and 800 °C, and elongated to 40%. During the hot tensile tests, various Fe-Zn intermetallic compounds were formed depending on the heating rate and the deformation temperature, and they were distinguished by X-ray diffraction and energy dispersive spectroscopy. δ and Γ were observed in the coating after 600 °C deformation regardless of heating rate. Since both phases did not liquefy at 600 °C, the steel was not embrittled. Heating to 700 °C sometimes produced δ which would be liquid at 700 °C. It was only produced at the highest heating rate and embrittled the steel. Γ was produced at 800 °C regardless of heating rate. Hence, the steel suffered from LME in all heating rate condition. Based on the results, the importance of selecting temperature and heating rate to study LME by hot deformation testing is discussed.