The iron-manganese TWIP steels, which contain 17-20% of manganese, derive their exceptional properties from a specific strengthening mechanism: twinning. The steels are fully austenitic and nonmagnetic, with no phase transformation. The formation of mechanical twins during deformation generates high strain hardening, preventing necking and thus maintaining a very high strain capacity.
The main groups of aluminum alloys which are the most often used in practice besides technically pure aluminum are AlMn, AlMg, AlMgMn, AlMgSi, AlZnMg, and AlZnMgCu alloys. These are wrought alloys which are shaped into products by rolling, extrusion, and forging. Each of the mentioned groups consists of numerous subgroups, depending on amounts of main and additional alloying elements, and they have tensile strength values varying in a wide range from 70 to 600 MPa.
TRIP-aided multiphase steels are a new generation of low-alloy steels that exhibit an enhanced combination of strength and ductility, thus satisfying the requirements of automotive industry for good formable high-strength steels.
After the thermal treatment of TRIP steels, a triple-phase microstructure is obtained, consisting of ferrite, bainite and retained austenite. TRIP steels are essentially composite materials with evolving volume fractions of the individual phases.