New Zn-coated steels enhance mechanical performance and reduce liquid metal embrittlement in press hardened steel.
New zinc‐coated steels suitable for press hardening have been developed to address the persistent issue of liquid metal embrittlement (LME) and to offer galvanic corrosion resistance to press‐hardened steel (PHS) substrates, not currently provided by the standard Al–Si‐coated steels. The newly designed Zn‐coated PHS alloys, containing 0.2–0.3 wt% C and elevated Mn levels (2–3 wt%), can be successfully press‐hardened from temperatures as low as 760 °C. Forming below the Γ‐peritectic temperature of the Fe–Zn system (782 °C) effectively suppresses LME by avoiding the presence of liquid Zn during deformation. Tensile testing of specimens extracted from hot‐stamped hat sections confirms that the mechanical performance of these alloys, achieving ultimate tensile strength values in the range of 1450–1500 MPa, is comparable to that of standard 22MnB5 parts formed at 900 °C. Notably, Zn‐induced LME macrocrack depths are reduced by 40–60% when forming is conducted at lower temperatures (≈780 °C). While small microcracks (≈10 μm) due to solid‐state Zn diffusion are still observed, their severity can be mitigated through design modifications such as increased corner radii or further optimization of alloy chemistry to enable even lower stamping temperatures. These findings demonstrate a promising pathway for developing LME‐resistant Zn‐coated PHS materials without compromising mechanical strength.
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Bhattacharya et al. (2025) studied this question.
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