High temperature compression tests for liquid metal embrittlement characterisation in steels

Materials Today Communications, vol. 45, pp. 111977

Abstract

A method was developed to investigate Zn-induced liquid metal embrittlement under simultaneous action of compressive stress and elevated temperature to simulate key aspects of the conditions that occur during resistance spot welding of steel sheet. We demonstrate the capability of the experimental set-up to analyse microstructural changes and phase transitions in the base substrate on the example of a medium Mn steel in combination with Zn. Major advantages of the testing methodology are high heating rates achieved through inductive heating and the application of a simplified compressive stress-state resembling key characteristics of spot welding conditions, i.e. indenting into the material as opposed to tensile testing. Furthermore, the method allows for post-mortem investigations and characterisation of Zn-enriched intermediate layers via specially prepared cross-sections on the mesoscale. This methodology was used to demonstrate that there were no notable changes in the reference material (IF steel) upon application of stress and temperature, whereas the medium Mn steel exhibited the formation of an intermediate layer at the liquid/solid interface, which constitutes an important mechanism with respect to liquid metal embrittlement. The methodology developed aims at unravelling the complicated influence of the stress-state and temperature during resistance spot welding under well-defined laboratory conditions by varying the Zn coating, temperature, and load independently, thus providing a means to uncover the fundamental mechanism of liquid metal embrittlement.

Authors 4

1. L. Ripperger corresponding Aachen Institute of Physical Metallurgy and Materials Physics

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Institute of Physical Metallurgy and Materials Physics, Kopernikusstrasse 14, 52074 Aachen, Germany

2. Thomas Burlet Aachen Institute of Physical Metallurgy and Materials Physics

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Institute of Physical Metallurgy and Materials Physics, Kopernikusstrasse 14, 52074 Aachen, Germany

3. Konstantin D. Molodov

   Salzgitter Group (Germany)

   Affiliation as printed

   Department of New Materials and Technologies, Salzgitter Mannesmann Forschung GmbH, Eisenhüttenstr. 99, 38239 Salzgitter, Germany

4. Stefanie Sandlöbes-Haut Aachen Institute of Physical Metallurgy and Materials Physics

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen University, Institute of Physical Metallurgy and Materials Physics, Kopernikusstrasse 14, 52074 Aachen, Germany