Microstructure and Local Mechanical Properties of the Heat-Affected Zone of a Resistance Spot Welded Medium-Mn Steel.

The properties of the heat-affected zone (HAZ) are reported to have a great influence on the mechanical performance of resistance spot welded advanced high strength steels. Therefore, in the present work, the HAZ of a medium-Mn steel is characterized regarding its microstructure and its mechanical properties depending on the distance to the fusion zone (FZ). In order to obtain the local mechanical properties of the HAZ, samples were heat-treated in a joule-heating thermal simulator using different peak temperatures to physically simulate the microstructure of the HAZ.

Microstructural evolution of a dual hardening steel during heat treatment.

Dual hardening steels combine precipitation of both secondary hardening carbides and intermetallic phases in a martensitic matrix. Due to this combination, the carbon content necessary to achieve high hardness levels can be reduced, resulting in a decreased amount of large and embrittling carbides. In this study, the influence of different heat treatments on microstructure evolution and secondary hardness is investigated.