Comparisons of microstructures and texture and mechanical properties of magnesium alloy fabricated by compound extrusion and direct extrusion

Abstract

A B S T R A C TIn this study, microstructure evolution, textures and mechanical properties of AZ61 magnesium alloy were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile tests. The samples were processed by a new compound extrusion (CE) which combines direct extrusion (DE) and two steps of equal channel anger extrusion (ECAE). The results show that CE process can refine the microstructure more effectively than the DE process. The CE-fabricated samples have a weaker texture (0002), and a more fine and homogeneous microstructures, which attributes to the additional two steps of ECAE in CE process. In CE process, twin dynamic recrystallization and rotational dynamic recrystallization occurred, which enhances the refinement of the grains and weakening of the texture. In addition, the samples fabricated by CE process display a higher tensile properties (yield strength, tensile strength and elongation) with an excellent balance of strength and tensile ductility. Based on this study, severe plastic deformation (SPD) techniques combining conventional DE and two steps ECAE into a single process are feasibility to improve the mechanical properties of AZ61 Mg alloy.

An Investigation on Microstructure, Texture and Mechanical Properties of AZ80 Mg Alloy Processed by Annular Channel Angular Extrusion

“…It can be considered that, in the postprocessed part, relatively dispersed fine β-particles are distributed at the grain boundaries and can effectively hinder the migration of dislocations and the deformation of the matrix, thereby increasing the material strength [26]. Finally, it should be considered that the appearance of texture weakening is of importance, which produced a large number of grains with relatively random orientation and soft orientation are favorable for basal slip at room temperature and, therefore, also has a certain improvement in material plasticity [5,6].…”

“…Magnesium (Mg) alloys, being among the lightest structural materials, have become a focus in the world due to their advantages [1,2], especially the high specific strength compared to other alloys [3,4]. In the past twenty years, Mg alloy structural components have been widely applied in automotive, aerospace, defense, and electronic industries, while more than 90% of them are in the as-cast state [5]. With the higher requirement of material strength, casting Mg alloy products have gradually failed to meet practical application needs.…”

“…In general, the mechanical properties of most metals can be effectively improved by modification of their microstructure via alloying, processing, heat treatment, and so on. Therefore, typically forming processes such as rolling, forging, and extrusion have been extensively employed to process Mg alloy materials [5,6]. However, conventional forming methods often fail to achieve significant refinement of microstructure and improvement of mechanical properties due to lower strain levels.…”

Modification of the anisotropy and strength differential effect of extruded AZ31 by extrusion-shear

“…al. [11,14] could also clearly refine the microstructure through ES. The textures in these two works show similar pole figures to those of the ES-135 sheet with slight ED contributions and tilting of the ND pole in ED basal planes.…”

“…achieved a high grain refining as well as good balance of strength and ductility in their investigations. However, they only considered the effect on the mechanical properties under tension in ED [9,11]. In other investigations Hu et.…”