Comportamiento mecánico de un acero avanzado de alta resistencia (AHSS) con un contenido medio de Mn en dos condiciones de laminación: caliente y tibio

Abstract

The microstructure before intercritical annealing of an AHSS

(Advanced High Strength Steel) with medium Mn content plays

an important role in the final mechanical properties, since the

transformations occurring during annealing modify phases,

composition, and morphology. The microstructural changes

that occur during intercritical annealing treatment of a

medium Mn steel were examined. Two starting material comes

from different conditions, hot rolling at 1200°C and warm

rolling (initial rolling at 1200°C and subsequent at 680°C).

The mechanical properties were related to the transformation

phenomena that occur in these steels, mainly TRIP

(Transformation Induced Plasticity) and TWIP (Twinning Induced

Plasticity) effects. The transformations were verified by SEM

(Scanning Electron Microscopy) and X-RD (X-Ray Diffraction).

Tensile strength values of 1111 MPa and 17% elongation were

obtained by hot rolling route. For the warm rolling route, 35%

deformation and a tensile strength of 1357 MPa were obtained.

The strain hardening curve was analyzed, showing the presence

of the TWIP effect subsequently “saw” behavior related to the

discontinuous TRIP effect. The mechanic properties values are

related to the difference in morphology phases present. An

acicular morphology of α/γ (ferrite/austenite) provides a higher

value of tensile strength, but low elongation percentage, and

a mixture of lamellar and globular morphologies, provides an

optimized combination of strength and ductility.