Role of Strain Reversal in Microstructure and Texture of Pure Al during Non-Monotonic Simple Shear Straining

The effect of reverse straining on the microstructure, texture, and hardness of the pure Al during the single cycle of the simple shear extrusion (SSE) process is investigated. Electron backscattering diffraction (EBSD), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM) are used for microstructural evaluations. Due to the nature of the SSE process, the direction of the shear is reversed in the second half channel. As a result, the mean misorientation angle, dislocation density, and hardness decrease. The grain size increases to some extent in the exit of the channel compared with that in the middle. The structural evolution during the single pass of SSE is described in terms of the dislocation cancelling, “untangling” of the cell walls and disintegration of the “forward” cell structure due to the reverse straining in the second half channel. Some simple shear components replace the first texture component in the middle of the channel. At the exit of the channel, the primary texture components appear somewhat confirming the strain reversal effect in the second half channel.

On the Production of Severely Deformed Workpieces in Large Scales: A Step Towards Industrialization

Improvement of the functional properties of aluminium and its alloys by grain refinement is an effective way to increase their applications. The capability of severe plastic deformation methods to produce ultrafine-grained materials has been well established. However, their industrial application is limited because of the required additional equipment and limitation of the product size. Due to the direct extrusion characteristic of the simple shear extrusion (SSE) method and consequently the minimal additional tools and expenses, SSE is a good candidate for commercialization. The aim of this research is to scale up the SSE products to facilitate their potential use in practical applications. To overcome the limitation on the length of the plunger and reduce the load of the SSE process, a design is proposed in the current research. Microstructural investigations and mechanical tests of commercial pure aluminium (AA1050) workpieces confirm the effectiveness of the proposed design on the grain refinement and its capability to reduce the processing load.

Microstructure and Texture Inhomogeneity after Large Non-Monotonic Simple Shear Strains: Achievements of Tensile Properties

In this study, for the first time, the effect of large non-monotonic simple shear strains on the uniformity of the tensile properties of pure Cu specimens was studied and justified by means of microstructural and textural investigations. A process called simple shear extrusion, which consists of two forward and two reversed simple shear straining stages on two different slip planes, was designed in order to impose non-monotonic simple shear strains. Although the mechanism of grain refinement is continuous dynamic recrystallization, an exceptional microstructural behavior and texture were observed due to the complicated straining path results from two different slip planes and two pairs of shear directions on two different axes in a cycle of the process. The geometry of the process imposes a distribution of strain results in the inhomogeneous microstructure and texture throughout the plane perpendicular to the slip plane. Although it is expected that the yield strength in the periphery reaches that of the center by retardation, it never reaches that value, which results in the different deformation modes of the center and the periphery. The occurrence of shear reversal in each quarter of a cycle results in the elimination of some of the boundaries, an increase in the cell wall thickness, and a decrease in the Taylor factor. Change in the shear plane in each half of a cycle leads to the formation of cell boundaries in a different alignment. Since the direction of the shear and/or the shear plane change frequently in a cycle, the texture of a sample after multi-cycles of the process more closely resembles a random orientation.