Research Article Obtaining Martensitic Structures during Thixoforming of Hypoeutectic Gray Cast Iron Lucas Bertolino Ragazzo, 1 Davi Munhoz Benati, 1 Rodolfo Lopez Nadal, 2 and Eugênio José Zoqui 1 1 Department of Materials and Manufacturing Engineering, Faculty of Mechanical Engineering, University of Campinas, 13083-860 Campinas, Brazil 2 Department of Materials and Manufacturing, Faculty of Mechanical Engineering, University of Oriente, 90400 Santiago de Cuba, Cuba Correspondence should be addressed to Eugˆ enio Jos´ e Zoqui; zoqui@fem.unicamp.br Received 1 June 2015; Revised 17 July 2015; Accepted 26 July 2015 Academic Editor: Olanrewaju Ojo Copyright © 2015 Lucas Bertolino Ragazzo et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e control of parameters such as liquid fraction, holding time, and cooling rate during thixoforming can help control the final microstructure of the thixoformed part, thus improving its mechanical properties. is study intended to investigate conditions required to obtain martensite in hypoeutectic gray cast iron at 3.1% CE (carbon equivalent) deformed in the semisolid state. Samples heated up to 1130, 1135, and 1145 ∘ C (liquid fractions of 10, 30, and 45%) were compressed into platens without any holding time (0 s). If a sample presented a martensitic structure for 0s holding time, new samples were retested at the same temperature for 30, 60, and 90s holding times. e die casting process was simulated by allowing the platens to become locked aſter hot compression. Samples that cooled in the locked platens were submitted to higher cooling rates than samples that cooled with the platens open and presented martensite instead of the conventional ferrite and pearlite. us, the factor that had the greatest influence on the formation of martensite was the cooling rate rather than stress. e thixoforming process presented good morphological stability, which is highly desirable for industrial applications. 1. Introduction ixoforming involves heating a material until it reaches the semisolid state followed by forming. e mechanical properties of the thixoformed product are determined by the final microstructure of the material used. Controlling some of the process parameters, such as liquid fraction (by adjusting the temperature in the semisolid state region), holding time (the time to ensure a homogeneous structure in the semisolid state), deformation, and cooling rate, can help control the final microstructure and promote martensitic transformation, thus improving the mechanical properties of the thixoformed parts [1, 2]. Steel and cast iron have been widely researched as potential raw materials for semisolid processing and have been shown to have a wide range of beneficial properties, such as good fluidity and stability in the semisolid state [3– 7]. Moreover, cast irons, which are low cost alloys, have a great variety of microstructures and, therefore, controllable mechanical properties, making them particularly suitable for applications where wear resistance is required [8]. Some cast irons, including hypoeutectic gray cast iron, have been suc- cessfully used as raw material for semisolid processing [9–12]. Martensitic transformation is a diffusionless shear trans- formation and involves no change in composition. In steels it is of particular importance, as it can confer an outstanding combination of strength and toughness. Many materials other than steel, such as cast irons and other Fe-C based alloys, nonferrous metals, pure metals, ceramics, minerals, inorganic compounds, solidified gases, and polymers, are now known to exhibit the same type of solid-state phase transformation, and in many the mechanism involved in the transformation is fully understood [13]. is paper seeks to investigate the conditions needed to produce a partial or full martensitic structure instead Hindawi Publishing Corporation Advances in Materials Science and Engineering Volume 2015, Article ID 170562, 7 pages http://dx.doi.org/10.1155/2015/170562