Advanced High Strength Steels (AHSS) for Automotive Applications − Tailored Properties by Smart Microstructural Adjustments

The average use of AHSS in car body design has increased significantly over the past 20 years. This growth is not only an average mass growth, but the variety of available grades and property combinations increase, thus supporting fit-for-purpose options for lightweight design. Numerous ideas for future implementation of the so called 2nd and 3rd generation AHSS are proposed. Currently, the concepts mainly focus on the improvement of strength AND ductility as the main drivers for lightweight design. Future concepts have to envision more than these two properties. In particular, formability is presently not well defined as it depends on the applied specific forming process during car manufacturing and, hence, requires different properties, for example, distinguishing local and global formability measures. This extends the known materials concepts to new further dimensions such as uniform elongation, n-value, stretch-flangeability, bending angle, hydrogen embrittlement. A new generation, referred to as “Generation 4.0” follows 3rd generation AHSS which, in turn, opens the manufacturers a new dimension for lightweight design of future vehicles with the use of highly sophisticated materials with exceptional tailored properties, where “tailored” regards to the carefully adjusted overall materials’ properties, instead of the spatially varying, as commonly used to describe “tailored blanks”.