Effect of severe plastic deformation on an extruded ZK60 magnesium alloy
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Effect of severe plastic deformation on an extruded ZK60 magnesium alloy Florina D. Dumitru1, György Deák1, Oscar F. Higuera-Cobos2 and José M. Cabrera-Marrero3,4 1 National Institute for Research and Development in Environmental Protection, 294 Splaiul Independentei, 060031, Bucharest, Romania. 2 Facultad de Ingeniería, Ingeniería Mecánica, Universidad del Atlántico, Barranquilla, Colombia. 3 Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica, Universidad Politécnica de Cataluña, Av. Diagonal 647, 08028 – Barcelona, España. 4 Fundación CTM Centre Tecnológic, Plaça de la Ciència 2, 08243, Manresa, España. ABSTRACT Equal channel angular pressing (ECAP) was carried out on extruded ZK60 magnesium alloy until an equivalent strain of ~4 (corresponding to 4 passes) at 523K following route Bc. The effect of the deformation on both microstructure and texture was investigated by analysis of inverse pole figures and pole figures respectively, determined by EBSD. Additionaly, the mechanical properties were evaluated through tensile tests. The ECAPed processed ZK60 alloy showed the presence of dynamic recrystallization (DRX) process, correlated with a strong basal fiber texture. The presence of pyramidal slip was also observed, which can be correlated with the presence on twin-oriented boundaries in the material. Both the grain size reduction and the existence of texture influenced the ductility of the magnesium alloy processed by ECAP, as the ductility of the ZK60 alloy after four ECAP passes increased two times in comparation with the initial (un-processed) material. INTRODUCTION Severe plastic deformation (SPD) techniques have been the focus of intense research in the last two decades, due to its advantages, like improvement of mechanical and physical properties caused by the induced grain refinement [1]. Among the SPD methods, equal channel angular pressing (ECAP) is considered one of the most promising for industrial applications, as different materials already show promising results: electrolytic copper, which can be used for power cables as it presents high mechanical properties and high electrical conductivity [2], pure titanium, used as a high strength biomaterial [3], and very low carbon steel of high strength and high weldability [4]. Another material with great potential for industrial applications is magnesium, as it provides excellent properties such as low densities, good castability and machinability, high specific strength and high specific stiffness among others [5]. However, due to its poor formability and reduced ductility at room temperature, magnesium and its alloys are not so frequently used in industry. For the HCP structure, the activated slip systems at room temperature is insufficient to accommodate uniform plastic deformation, as magnesium only allows three independent active slip systems at basal plane for the magnesium alloys. The deformation mechanisms are: slip on the basal {0002} 1120 , prismatic {10 1 0} 1120 and pyramidal {10 1 1} 1120 systems. During ECAP processing, other non
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