Effect of Ti Microaddition on Cavitation Behavior During Uniaxial Hot-Tensile of Fe-22Mn-1.5Al-1.3Si-0.5C Austenitic TWI
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Effect of Ti Microaddition on Cavitation Behavior During Uniaxial Hot-Tensile of Fe-22Mn-1.5Al-1.3Si-0.5C Austenitic TWIP Steel Antonio E. Salas-Reyes1,2, Ignacio Mejía1 and José M. Cabrera3,4 1 Instituto de Investigaciones Metalúrgicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Mich., 58066, México. E-mail: [email protected], [email protected] 2 Ingeniería en Metalúrgica, Universidad Politécnica de Juventino Rosas, Comunidad de Valencia, Santa Cruz de Juventino Rosas, Gto., 38253, México. 3 Departament de Ciència dels Materials i Enginyeria Metal•lúrgica, ETSEIB – Universitat Politècnica de Catalunya. Av. Diagonal 647, 08028 – Barcelona, Spain. 4 Fundació CTM Centre Tecnològic, Plaça de la Ciència, 2, 08243– Manresa, Spain. ABSTRACT It is well-known that metal and alloys develop internal cavities when subjected to uniaxial or multiaxial tensile strains at elevated temperature. In most cases, cavitation may lead to premature failure during forming. Therefore, damage and fracture behavior imposes significant limitations in hot metal-forming processes. Although high-Mn austenitic TWIP steels exhibit a unique combination of strength and ductility, cavitation during hot working is one issue that must be tackled. The aim of this research work is to determine the effect of Ti microaddition on cavity mechanisms of Fe-22Mn-1.5Al-1.3Si-0.5C TWIP steel under uniaxial hot-tensile condition at 800 °C and constant true strain rate of 10-3 s-1. For this purpose, light optical (LOM) and scanning electron (SEM) microscopies and image analysis were applied to quantify cavities formation along longitudinal section of deformed samples near to the fracture surface. The number of cavities greater than 10 µm (critical length) in non-microalloyed and Ti microalloyed TWIP steels were 2.75 and 3.75 cavities/mm2, respectively. On the other hand, average cavity area was 125 and 152 µm2, respectively. Both TWIP steels showed cavities type “r”, “l” and “A”. Finally, Ti microaddition to TWIP steel resulted in a predominant brittle fracture behavior due to finer grain-boundary precipitation, which weakens grains cohesion and accelerates crack growth by grain-boundary sliding. In this case, crack growth behavior is explained in terms of a void interconnection mechanism. INTRODUCTION Fe-Mn-C twinning-induced plasticity (TWIP) steels represent a novel grade of advanced high-strength and formable austenitic steels with high potential for automotive and related sheetforming applications [1]. In metal forming processes, the product shapes are produced by plastic deformation. Essentially, hot deformation is an important processing step during the manufacture of most metal products, affecting the microstructure and the mechanical properties [2]. The concern of material suppliers is also focused on the processability of the material during manufacturing, which is often specified in terms of formability. The margins of formability are mainly dictated by the failure behavior of materials as well as its precursor: strain location. From
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