Caracterización dinámica de los cambios microestructurales en barras de aceros dúplex SAF 2205 utilizando la dimensión de información

Abstract

RESUMEN:En el presente estudio se evalúa el comportamiento dinámico de las señales ultrasónicas de muestras de acero dúplex SAF 2205 (UNS31803), sometidos a tratamientos de envejecimiento a 875 y 950 °C. En el primer tratamiento se promueve la precipitación de la fase sigma y en el segundo su disolución. Los resultados obtenidos por microscopía óptica indican que la cantidad relativa de la fase sigma aumenta progresivamente con el tiempo de envejecimiento a 875 °C, observándose la transformación de la fase ferrita en fase sigma y en austenita secundaria. Por otra parte, a medida que se aumenta el tiempo de tratamiento a 950 °C, se observa una reducción del porcentaje de fase sigma y un aumento de la fase ferrítica. El estudio propone evaluar en el ámbito de sistemas dinámicos la influencia de las fases microestructurales en el comportamiento de las señales y su dependencia con las pérdidas de energía, que ocurren en el sistema por efecto de los tratamientos térmicos, utilizando la teoría del caos determinista. Para caracterizarlos se emplea la representación del espacio de fases dinámicas y el cálculo de la dimensión de información. Los resultados obtenidos muestran una mayor correlación entre la dimensión de información y el coeficiente de atenuación, en comparación con las fracciones de fase. No obstante, la eficiencia de este tipo de estudio depende de la frecuencia seleccionada durante la evaluación del material. SUMMARY: Dynamics characterization of microstructural changes in bars of duplex steels SAF 2205 using the information dimension.This study evaluates the ultrasonic signals behavior of a duplex stainless steel SAF 2205 (UNS S31803) after aging treatments at 875 and 950 °C. The first treatment promotes the precipitation of the sigma phase and the second, its dissolution. The microstructural evaluation was carried out by optical microscopy. The results showed an increase of the sigma phase fraction and the secondary austenite with the time of aging treatment at 875 °C. On the other hand, increasing the time of treatment at 950 °C promotes a reduction of the sigma phase and the corresponding increase of the ferrite phase fraction. The study proposed to evaluate in the dynamical system field the influence of microstructural phases in the signals behavior and their dependence on the energy losses occurring in system during heat treatment, by deterministic chaos theory. To accomplish characterization, algorithm employs the representation of dynamic phase space and the information dimension estimate. The results show a higher correlation between the information dimension and the attenuation coefficient in comparison with the phase fractions. However, the efficiency of this type of study will depend on the frequency selected for the evaluation of the material.

Effect of alloying and microstructure on formability of advanced high-strength steels processed via quenching and partitioning

“…The development of materials for modern automotive industry is defined by numerous and often contradictory constraints including manufacturing capabilities of the industrial processing lines, high mechanical strength, lightweighting of parts and structural components, sufficient formability for metalforming operations and many others [1]. The steel manufacturers have continuously been presenting innovative solutions to the automotive industry, since steels have the ability to adapt to the changing requirements [2][3][4][5]. Over the past decades, significant research efforts have been directed towards the development of several types of advanced high strength steels (AHSSs) [3], since they provide an opportunity for the manufacturing of cost-effective, light-weight parts with improved safety and optimized environmental performance [4,6,7].…”

Effect of Q&P parameters on microstructure development and mechanical behaviour of Q&P steels

“…For this purpose, the steel industry is continuously presenting innovative solutions to the automotive industry, since this material has the ability to adapt to the changing requirements. In particular, the past few decades have witnessed a significant research effort directed towards the development of Advanced High-Strength Steel (AHSS) grades, as they provide an opportunity for the development of cost-effective and light-weight parts with improved safety and optimized environmental performance for automotive applications (Bhadeshia, 1999;De Moor et al, 2010;Caballero et al, 2013;Rodríguez et al, 2014). These research strategies are based on the development of microstructures consisting of ultrafine microconstituents formed in non-equilibrium conditions, such as martensite or bainite, in combination with Retained Austenite (RA) (Santofimia et al, 2008;Caballero et al, 2009;Garcia-Mateo et al, 2012).…”