TY - JOUR

T1 - Revealing joining mechanism in refill friction stir spot welding of AZ31 magnesium alloy to galvanized DP600 steel

AU - Fu, Banglong

AU - Shen, Junjun

AU - Suhuddin, Uceu F.H.R.

AU - Pereira, Ayrton A.C.

AU - Maawad, Emad

AU - dos Santos, Jorge F.

AU - Klusemann, Benjamin

AU - Rethmeier, Michael

N1 - Banglong Fu is gratefully acknowledging the funding of China Scholarship Council (Grant No. 201506220158). The valuable suggestions from Ms. Changyun Sun (Ludwig-Maximilians-Universit?t M?nchen, LMU) are greatly appreciated. The authors are grateful to Prof. Dr. Norbert Hort and Daniel Strerath (Institute of Metallic Biomaterials, Helmholtz-Zentrum Hereon) for the help in determining the chemical compositions of BMs. We acknowledge Deutsches Elektronen-Synchrotron DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of the research were carried out at the High Energy Materials Science (HEMS) of the Helmholtz-Zentrum Hereon using P07B beamline. All the raw/processed data required to reproduce these findings are available from the authors upon reasonable requests.

PY - 2021/11/1

Y1 - 2021/11/1

N2 - The application of magnesium (Mg) inevitably involves dissimilar welding with steel. A novel solid state spot welding method, refill friction stir spot welding (refill FSSW), was utilized to weld AZ31 Mg alloy to galvanized DP600 steel. Although Mg/Fe is an immiscible alloy system, defect-free welds with high strength were successfully obtained in a wide parameter window. The results of microstructure, interfacial reactions, and mechanical properties are reported to reveal the underlying joining mechanism. Due to the melting of Zn coating and subsequent Mg-Zn reactions, Mg-Zn eutectic and intermetallic compounds were detected within welds. Heterogeneous interfacial reactions occur along Mg/steel interface, and the relationship between interfacial structure and fracture behavior was investigated. The joining mechanism is associated with Zn coating and Fe-Al layer: 1) the presence of Zn coating is beneficial for achieving high-quality welding between Mg and steel, it protects the interface from oxidation and contributes to brazing of the weld; 2) the Al present in Mg alloy reacts with Fe, resulting in the growth of Fe-Al layer, which contributes to the diffusion bonding in the interface. The overall results clearly show that refill FSSW is a competitive welding method for joining Mg and galvanized steel.

AB - The application of magnesium (Mg) inevitably involves dissimilar welding with steel. A novel solid state spot welding method, refill friction stir spot welding (refill FSSW), was utilized to weld AZ31 Mg alloy to galvanized DP600 steel. Although Mg/Fe is an immiscible alloy system, defect-free welds with high strength were successfully obtained in a wide parameter window. The results of microstructure, interfacial reactions, and mechanical properties are reported to reveal the underlying joining mechanism. Due to the melting of Zn coating and subsequent Mg-Zn reactions, Mg-Zn eutectic and intermetallic compounds were detected within welds. Heterogeneous interfacial reactions occur along Mg/steel interface, and the relationship between interfacial structure and fracture behavior was investigated. The joining mechanism is associated with Zn coating and Fe-Al layer: 1) the presence of Zn coating is beneficial for achieving high-quality welding between Mg and steel, it protects the interface from oxidation and contributes to brazing of the weld; 2) the Al present in Mg alloy reacts with Fe, resulting in the growth of Fe-Al layer, which contributes to the diffusion bonding in the interface. The overall results clearly show that refill FSSW is a competitive welding method for joining Mg and galvanized steel.

KW - Galvanized steel

KW - Magnesium alloy

KW - Mechanical properties

KW - Microstructure

KW - Multi-materials joining

KW - Refill friction stir spot welding

KW - Engineering

UR - http://www.scopus.com/inward/record.url?scp=85111319509&partnerID=8YFLogxK

U2 - 10.1016/j.matdes.2021.109997

DO - 10.1016/j.matdes.2021.109997

M3 - Journal articles

AN - SCOPUS:85111319509

VL - 209

JO - Materials and Design

JF - Materials and Design

SN - 0264-1275

M1 - 109997

ER -