Influence of silicon addition on intercritical annealing process and tensile properties of medium Mn steel
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Influence of silicon addition on intercritical annealing process and tensile properties of medium Mn steel Yan Li1, Runxun Wang2, Baofeng Wang2, and Wei Ding2,* 1
Bayan Obo Multi-Metallic Resource Comprehensive Utilization Key Laboratory, Inner Mongolia University of Science and Technology, Baotou 014010, People’s Republic of China 2 School of Material and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, People’s Republic of China
Received: 17 April 2020
ABSTRACT
Accepted: 9 August 2020
This paper presents research on the equilibrium phase fractions, microstructure, and tensile properties of a 0.2C–5Mn–1.5Al (mass %) steel with 0 or 0.5 (mass %) Si addition after intercritical annealing (IA), using thermodynamic simulation, scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, and uniaxial tensile testing. The research results show that the addition of 0.5 Si (mass %) has no significant effect on the equilibrium phase fraction but influences the optimal IA temperature. Different IA temperatures result in the retained austenite having different morphologies. The retained austenite in the 730 °C sample (0.5 Si) has two different morphologies— polygonal and lath—while the 760 °C sample (0 Si) has only polygonal retained austenite. The optimal tensile properties of the 0.5 Si steel are better than those of the 0 Si steel due to the solution strengthening effect of Si and the higher stability of retained austenite. The tensile properties of the investigated 0.5 Si steel are excellent, with a tensile strength of over 1 GPa, elongation over 42.00%, and strength 9 ductility over 42 GPa%.
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Introduction In the past several decades, advanced high-strength steels (AHSS) have been widely applied in the automobile industry to meet the body-in-white weight reduction strategies pursued globally by car manufacturers for fuel economy and vehicle safety [1, 2].
Handling Editor: David Balloy.
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https://doi.org/10.1007/s10853-020-05330-x
AHSS have developed from the first generation to the third generation [3, 4], which have mechanical properties that exceed those of the first-generation AHSS and a potentially lower cost than that of the second-generation AHSS. Medium Mn steels with a manganese content of 3–12 (mass %) are considered a powerful candidate material for third-generation AHSS and have been
J Mater Sci
extensively investigated [5–13]. Transformation from austenite to martensite during tensile deformation, that is, transformation-induced plasticity (TRIP), is one of the prominent strategies used to obtain the desired tensile properties for the medium Mn TRIP steel [14, 15]; therefore, the fraction and stability of the austenite are very important. The Fe–C–Mn medium Mn steels, with increased content of Mn compared with the first-generation AHSS, effectively stabilize austenite and increase the retained austenite fraction [8, 16, 17]
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