Liquid Metal Embrittlement of Advanced High Strength Steel: Experiments and Damage Modeling

Area of Science:

• Materials Science
• Mechanical Engineering
• Manufacturing Processes

Background:

• Advanced high strength steels with high ductility (AHSS-HD) are crucial for lightweight automotive designs.
• Galvanized AHSS-HD can experience liquid metal embrittlement (LME) during thermomechanical loading, like resistance spot welding, causing significant ductility loss.
• Understanding LME in dual phase steels (DP1200HD) is critical for ensuring structural integrity.

Purpose of the Study:

• To investigate the influence of thermal and mechanical loading on LME in DP1200HD steel.
• To develop and validate a machine learning-based LME damage model for galvanized AHSS-HD.
• To predict the occurrence and intensity of LME during welding processes.

Main Methods:

• Systematic isothermal hot tensile testing using a Gleeble® 3800 thermomechanical simulator.
• Application of symbolic regression for machine learning-based LME damage model calibration.
• Finite element (FE) implementation and validation of the developed LME damage model.

Main Results:

• Experimental data characterized the LME behavior of DP1200HD steel under varying temperature, plastic strain, and strain rate conditions.
• A calibrated LME damage model accurately predicted the governing quantities influencing embrittlement.
• FE validation confirmed the model's ability to predict the local position and intensity of LME in tensile samples and spot welds.

Conclusions:

• The developed machine learning LME damage model effectively captures the critical factors governing embrittlement in galvanized DP1200HD steel.
• The validated model provides a reliable tool for predicting and mitigating LME during resistance spot welding in the automotive industry.
• This research contributes to safer and more reliable manufacturing of lightweight, high-strength steel components.