Development of Advanced High Strength Steels (AHSS) for Automobiles: A Review on Design Criteria

Improved fuel economy and emissions, leads to a
growing trend to produce steels with high specific
strength in vehicles. The high-strength, high-ductility
characteristics of AHSS come from the metals’ unique
microstructures. Where most steels have primarily
one microstructural phase, like ferrite, AHSS typically
has a combination of martensite, bainite, austenite
and ferrite phases. Each microstructural phase has a
different crystalline or molecular structure. For instance,
ferrite has a body-centered-cubic (BCC) structure, and
martensite has a body-centered-tetragonal structure.
Each structure has its own set of physical properties
due to the forces within the crystals and the densities
with which atoms are packed in a crystal cell. Various
research studies have shown that proper application
of AHSS can cut a vehicle’s weight between 10 and
25%. When fuel economy is paramount, the 5% fueleconomy
boost a 10% reduction in weight provides is
a nice carrot.