Texture formation process of 6063-type aluminium alloy during hot extrusion

This study investigated the texture formation process of A6063 alloy hot extruded material using electron backscatter diffraction (EBSD) measurements. The cube component that becomes the main orientation during hot extrusion was formed near the bearing inflow in the extrusion chamber and grew with continuous recrystallization. The Goss component with the same ED // <100> relationship as the cube component was not formed in the chamber or the bearing but was formed by discontinuous recrystallization after passing through the bearing. The TD // <111> orientation component of the surface layer was formed in the bearing and then grew with discontinuous recrystallization. However, because the internal cube and Goss components expanded preferentially, the surface layer TD // <111> components were replaced by the cube and Goss components after passing through the bearing. The cubic texture formation of extruded aluminium alloys is noted to be analogous to the formation of rolling sheet materials, formed by recovery and recrystallization from a plane strain deformation structure. However, for the A6063 alloy extruded under conditions close to industrial production, the cube components were mainly formed by recovery and continuous recrystallization.

Solution Behavior near Envelopes of Characteristics for Certain Constitutive Equations Used in the Mechanics of Polymers

The present paper deals with plane strain deformation of incompressible polymers that obey quite a general pressure-dependent yield criterion. In general, the system of equations can be hyperbolic, parabolic, or elliptic. However, attention is concentrated on the hyperbolic regime and on the behavior of solutions near frictional interfaces, assuming that the regime of sliding occurs only if the friction surface coincides with an envelope of stress characteristics. The main reason for studying the behavior of solutions in the vicinity of envelopes of characteristics is that the solution cannot be extended beyond the envelope. This research is also motivated by available results in metal plasticity that the velocity field is singular near envelopes of characteristics (some space derivatives of velocity components approach infinity). In contrast to metal plasticity, it is shown that in the case of the material models adopted, all derivatives of velocity components are bounded but some derivatives of stress components approach infinity near the envelopes of stress characteristics. The exact asymptotic expansion of stress components is found. It is believed that this result is useful for developing numerical codes that should account for the singular behavior of the stress field.

Texture Gradient in a Rectangular Extruded Al60Mg40 Metal Matrix Composite

By applying cold extrusion, an elemental metal powder composite Al60Mg40 was prepared. The texture gradient was measured over the cross-section of the extrusion profile using synchrotron radiation while the bulk texture was obtained by neutron diffraction. The aluminum phase shows a typical texture component of plane-strain deformation in the middle part of the sample and a uniaxial deformation texture at the surface. In the central region of the extruded bar, the (0002) Mg pole figure shows a split along the extrusion direction (±ED), which also has been observed in rare-earth containing magnesium alloys. These two poles twist towards the transverse direction on moving towards the surface of the extruded bar; one pole moves to +TD and the other one to −TD. The angle of twist increases towards the TD surface.

On the Difference of Subsurface Deformation Obtained by Image Correlation Technique From That of Plane Strain Deformation in Orthogonal Metal Cutting

Subsurface deformation in orthogonal metal cutting process is nowadays widely determined by image correlation techniques. To get clearer images of the cutting process, two methods were usually adopted to reduce workpiece material side flow in the literature. One is inducing a weak inclination angle of the cutting tool; the other is to restrict material side flow by a piece of thick glass. However, the differences between the subsurface deformation determined by observing the side surfaces in these two methods and that of plane strain deformation has not been studied yet. Therefore, this paper aims to study the differences of subsurface deformation obtained by these two methods quantitatively through numerical methods. It is found that the restrict side flow method surpasses the inducing an inclination angle method; inducing an inclination angle method will produce larger discrepancy than the side surface of typical orthogonal cutting which stands for observing the side surface directly. Besides, restrict material side flow method surpasses inducing an inclination angle method in the aspect of strain distribution across the width direction. To reduce the differences further, a new method called split-workpiece method based on the bonded-interface technique is proposed in this paper. To validate the effectiveness of this method, numerical comparisons between the subsurface deformation produced by the proposed method and that of the plane strain deformation are made. The results show that the subsurface deformation produced by the proposed method is much closer to that of plane strain deformation than the previous two methods.