TY - JOUR

T1 - Liquid Metal Embrittlement of Advanced High Strength Steel

T2 - Experiments and damage modeling

AU - Prabitz, Konstantin

AU - Asadzadeh, Mohammad Z.

AU - Pichler, Marlies

AU - Antretter, Thomas

AU - Beal, Coline

AU - Schubert, Holger

AU - Hilpert, Benjamin

AU - Gruber, Martin

AU - Sierlinger, Robert

AU - Ecker, Werner

N1 - Publisher Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

PY - 2021/9/21

Y1 - 2021/9/21

N2 - In the automotive industry, corrosion protected galvanized advanced high strength steels with high ductility (AHSS-HD) gain importance due to their good formability and their lightweight potential. Unfortunately, under specific thermomechanical loading conditions such as during resistance spot welding galvanized, AHSS-HD sheets tend to show liquid metal embrittlement (LME). LME is an intergranular decohesion phenomenon leading to a drastic loss of ductility of up to 95%. The occurrence of LME for a given galvanized material mainly depends on thermal and mechanical loading. These influences are investigated for a dual phase steel with an ultimate tensile strength of 1200 MPa, a fracture strain of 14% and high ductility (DP1200HD) by means of systematic isothermal hot tensile testing on a Gleeble® 3800 thermomechanical simulator. Based on the experimental findings, a machine learning procedure using symbolic regression is applied to calibrate an LME damage model that accounts for the governing quantities of temperature, plastic strain and strain rate. The finite element (FE) implementation of the damage model is validated based on the local damage distribution in the hot tensile tested samples and in an exemplary 2-sheet resistance spot weld. The developed LME damage model predicts the local position and the local intensity of liquid metal induced cracking in both cases very well.

AB - In the automotive industry, corrosion protected galvanized advanced high strength steels with high ductility (AHSS-HD) gain importance due to their good formability and their lightweight potential. Unfortunately, under specific thermomechanical loading conditions such as during resistance spot welding galvanized, AHSS-HD sheets tend to show liquid metal embrittlement (LME). LME is an intergranular decohesion phenomenon leading to a drastic loss of ductility of up to 95%. The occurrence of LME for a given galvanized material mainly depends on thermal and mechanical loading. These influences are investigated for a dual phase steel with an ultimate tensile strength of 1200 MPa, a fracture strain of 14% and high ductility (DP1200HD) by means of systematic isothermal hot tensile testing on a Gleeble® 3800 thermomechanical simulator. Based on the experimental findings, a machine learning procedure using symbolic regression is applied to calibrate an LME damage model that accounts for the governing quantities of temperature, plastic strain and strain rate. The finite element (FE) implementation of the damage model is validated based on the local damage distribution in the hot tensile tested samples and in an exemplary 2-sheet resistance spot weld. The developed LME damage model predicts the local position and the local intensity of liquid metal induced cracking in both cases very well.

KW - Advanced high strength steel

KW - Damage modeling

KW - Finite element modeling

KW - Genetic programming

KW - Liquid metal embrittlement

KW - Machine learning

KW - Resistance spot welding

KW - Symbolic regression

UR - http://www.scopus.com/inward/record.url?scp=85115655638&partnerID=8YFLogxK

U2 - 10.3390/ma14185451

DO - 10.3390/ma14185451

M3 - Article

AN - SCOPUS:85115655638

VL - 14.2021

JO - Materials

JF - Materials

SN - 1996-1944

IS - 18

M1 - 5451

ER -