Abstract
High manganese TWIP steel belongs to the second generation of advanced high strength steels. During the production of strip material, the microstructure and hence the mechanical properties of TWIP steel can be adapted to the specific needs of crash relevant structures. Whereas typically the whole steel strip is heat-treated after cold rolling, a local heat treatment can be applied to tailor the properties accordingly. In this work, a method is presented to identify a suitable process window for the local laser heat treatment of TWIP steel. The material is strain hardened and afterwards heat-treated at various temperatures for a short time. The influence of the respective heat treatment on microstructure and mechanical properties is evaluated and the most appropriate heat treatment is then reproduced using laser heating. To verify the effect of a local laser heat treatment at a structural component, crash boxes with different heat treatment patterns were produced and tested. The dynamic crash tests show that the local heat treatment can be used to improve the crash behavior of structural components. In addition, their deformation path can be influenced by using adapted heat treatment patterns and the crash behavior can be controlled.
Highlights
High manganese Twinning Induced Plasticity (TWIP) steel belongs to the second generation of advanced high strength steels
The dynamic crash tests show that the local heat treatment can be used to improve the crash behavior of structural components
Advanced high strength steels (AHSS) have a great potential as lightweight material in the automotive industry compared to alternative materials as aluminum, plastics or carbon fiber reinforced plastics [1]
Summary
Advanced high strength steels (AHSS) have a great potential as lightweight material in the automotive industry compared to alternative materials as aluminum, plastics or carbon fiber reinforced plastics [1]. The approach of a tailored heat treatment can be used to improve the crash behavior of structural components made of high manganese steel. The goal is to show for a structural component that it is possible to improve and locally tailor the mechanical properties of AHSS based on a shortened process chain including local laser heat treatment, and to reveal completely new design options. This yields the following research questions: How can the microstructure and mechanical properties of high manganese TWIP steel be influenced by a short-time (laser) heat treatment?. Can the energy absorption capacity be increased by adapting the material properties in the different areas to the external loading condition during deformation?
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