Mechanical and Microstructural Characterization of an Aluminum Bearing Trip Steel

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TRIP-assisted CMnSiAl steels with a fully martensitic initial microstructure have been studied in order to investigate the effect of partial substitution of Si by Al. The steel was fabricated by casting in a sand mold, hot forged, homogenizing, hot rolling, cold rolling, intercritical annealing, and finally, an isothermal bainitic treatment. During the intercritical annealing at 1023 K (750 °C) for 420 s, a matrix with a microstructure consisting of 50% proeutectoid ferrite was induced and after isothermal treatment at 663 K (390 °C) for 300 s, a microstructure of ferrite, bainite, and retained austenite was obtained. This austenite was carbon enriched and therefore stabilized, with an Ms lower than original austenite, before bainitic treatment. Microstructure and tensile properties have been analyzed, comparing these results with those corresponding to a commercial TRIP 780 steel. During tensile tests, retained austenite changes from 8.1 to 1.9%vol, with a total elongation of 23.2%, which demonstrates the TRIP effect. Texture analysis showed a weak γ-fiber in the steel, which deteriorates the drawing properties of the steel. The maximum elongation during the tensile test of this steel was obtained at 323 K (50 °C), correlating with the TRIP effect present in steel, which is favored when working within the critical zone of temperatures Msσ and Md. The results show that partial substitution of Si by Al decreases yield stress, ultimate tensile strength, increases the total elongation, and decreases the temperature for maximum elongation, related to TRIP 780.

Section: Due To Sample M390-300 Showing the Best Combination Between ...supporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Effect of Bainitic Isothermal Treatment on the Microstructure and Mechanical Properties of a CMnSiAl TRIP Steel

Guzmán

Monsalve

2022

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“…Some researchers have investigated the effect of Al addition on bainitic transformation [5,[12][13][14][15][16][17]. For example, Jimenez-Melero et al [5] and Zhao et al [12] reported that the addition of Al significantly increases the chemical driving force for the formation of bainitic ferrite plates and shortens the austenite-to-bainite transformation time.…”

Section: Introductionmentioning

confidence: 99%

The Effects of Cr and Al Addition on Transformation and Properties in Low‐Carbon Bainitic Steels

Tian

Zhou

et al. 2017

Three low-carbon bainitic steels were designed to investigate the effects of Cr and Al addition on bainitic transformation, microstructures, and properties by metallographic method and dilatometry. The results show that compared with the base steel without Cr and Al addition, only Cr addition is effective for improving the strength of low-carbon bainitic steel by increasing the amount of bainite. However, compared with the base steel, combined addition of Cr and Al has no significant effect on bainitic transformation and properties. In Cr-bearing steel, Al addition accelerates initial bainitic transformation, but meanwhile reduces the final amount of bainitic transformation due to the formation of a high-temperature transformation product such as ferrite. Consequently, the composite strengthening effect of Cr and Al addition is not effective compared with individual addition of Cr in low-carbon bainitic steels. Therefore, in contrast to high-carbon steels, bainitic transformation in Cr-bearing low-carbon bainitic steels can be finished in a short time, and Al should not be added because Al addition would result in lower mechanical properties.

“…These paths were obtained by (i) heating the samples to two temperatures within the fully austenitic range, followed by an intercritical annealing treatment (IAT) to form equal fractions of ferrite and austenite; and (ii) heating-up directly from room temperature to the intercritical range to transform the microstructure. The intercritical temperature was obtained from a previous work [29]. All three paths were followed by an isothermal bainitic treatment (IBT), also known as austempering: a salt bath and subsequent water quenching.…”

Section: Steel Manufacturing and Heat Treatmentsmentioning

confidence: 99%

Microstructure-Based Constitutive Modelling of Low-Alloy Multiphase TRIP Steels

Salinas‐Rodríguez

Celentano

Carvajal

et al. 2019

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The microstructure of low-alloy multiphase transformation-induced plasticity (TRIP) steels consists of ferrite, bainite, and metastable retained austenite, which can be transformed into martensite by plastic deformation. In some cases, residual martensite can be present in the initial microstructure. The mechanical behavior of these steels depends on the interaction between the intrinsic characteristics of the existing phases and the austenite stability. Due to these factors, the definition of their true stress-strain flow law is complex. This work presents the mechanical characterization of a phenomenological constitutive stress-strain flow law based on the Bouquerel et al. model, as evaluated for three TRIP steels of the same composition but undergoing different heat treatments. Morphological aspects of the existing phases, austenite stability, and suitable mixture laws between phases are considered. The model is found to accurately reproduce a true stress-strain flow law obtained under tensile uniaxial conditions and provide detailed information on the effective stress strain partition between the existing phases.