Metallographic, Structural and Mechanical Characterization of REM-Containing Fe-30Mn-8Al-1.8C Low Density Steel in As-Ca
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.11
Metallographic, Structural and Mechanical Characterization of REM-Containing Fe-30Mn-8Al1.8C Low Density Steel in As-Cast Condition G.Y. Díaz-Martínez1, I. Mejía1, V. García-García1, A. Bedolla-Jacuinde1 1 Departamento de Metalurgia Mecánica, Instituto de Investigación en Metalurgia y Materiales, Universidad Michoacana de San Nicolás de Hidalgo, Edificio “U-3” Ciudad Universitaria, 58030 Morelia, Michoacán, México. E-mail: [email protected]
ABSTRACT
Recently, low-density steels have received increased attention as promising alternatives for automotive applications of the next generation of Advanced High-Strength Steels (AHSS), considering that vehicle´s weight decrease has been the subject of intense interest. It is wellknown that the addition of rare earth metals (REM) has a remarkable effect on shape control and the modification of inclusions. Also, REM additions affect the grain size refinement as well as the tendency to form oxides and sulfides. The aim of this research work was to determine the effect of REM (Ce, La) addition on the microstructure and mechanical properties of the Fe-30Mn-8Al-1.8C low-density steel in as-cast condition. In order to clarify the REM effect on the Fe-Mn-Al-C system, non-microalloyed (LD-NM) and REM microalloyed (LD-REM) specimens were examined in detail by means of light optical and scanning electron microscopy for microstructural characterization. In the same way, the primary and secondary phases founded in the studied steels were identified by X-ray diffraction (XRD). Meanwhile, in order to evaluate the mechanical properties, ten microhardness measurements were carried out on the overall bulk by the Vickers hardness testing. In general, the results showed a dendritic refinement effect due to the addition of REM to low-density steel. REM acted as effective inoculants agents which reduced the primary and secondary arm spacing. Also, the strong segregation tendency at the grain boundaries in the liquid phase was limited. XRD profiles revealed the presence of austenite, ferrite, κ and DO3 phases. Low density steel microalloyed with REM showed a moderate increase in hardness compared to the non-microalloyed steel in the as-cast condition.
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INTRODUCTION Low-density (LD) steels (Fe-Mn-Al-C) have an extraordinary combination of high strength and large elongation. These light-weight alloys can be classified according to the major constituent phase: i) ferritic (α), ii) austenitic (γ) and iii) triplex steels (α + γ + κ-carbides) [1]. LD steels exhibit a typical chemical composition with Mn content between 20 and 30 wt%, Al addition up to 10 wt%, and C content between 0.5 and 1.8 wt% [2]. The reduction in mass density is due to the high Al content. It is well-known that approx
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