Microstructure and properties of copper and aluminum alloy 3003 heavily worked by equal channel angular extrusion

Abstract

A technique invented in the former Soviet Union and recently introduced in the United States, called equal channel angular extrusion (ECAE), produces intense and uniform deformation by simple shear and is applied to 25 ϫ 25 ϫ 152-mm billets of Cu 101 and Al 3003. Microcrystalline structures with a grain size of 0.2 to 0.4 m are created during room-temperature multipass ECAE deformation for true strains lying in the range ε ϭ 2.31 to 9.24. Evidence shows that intense simple shear deformation promotes dynamic or continuous recrystallization by subgrain rotation. The effects of the number of extrusion passes and deformation route for Cu 101, and the deformation route after four passes for Al 3003, are studied. Increasing the number of ECAE passes in Cu 101 causes strength to reach saturation and grain refinement stabilization after four passes (true strain of 4.68), and subgrain misorientation to increase as the number of passes increases. For multipass ECAE with billet orientation constant (route A) or rotated 90 deg between all passes (route B), two levels of structures are created inside the original grains: shear bands (first level) and very fine subgrains (second level) within the shear bands. For a billet rotation of 180 deg between passes (route C), an unusual event is observed. At each even numbered pass, shear bands nearly disappear and only subgrains are present inside the original grains. Route B gives the highest strength, whereas route C produces a more equiaxed and stable microstructure. Subsequent static recrystallization increases the average grain size to 5 to 10 m.

Properties and Nanostructures of Materials Processed by SPD Techniques

“…The grain size distribution usually follows a lognormal statistical function [24]. ECAP, especially route B C , in which the work-piece is rotated 90° clockwise between adjacent passes, can produce equiaxed grains (see Fig.…”

Equal Channel Angular Extrusion Progress Report for March 1998 - May 1999

“…It has been shown that four or more passes creates a homogeneous and stable microstructure. 2 In addition, by choosing appropriate billet orientations as it enters the extrusion die on each pass, a variety of microstructures and textures can be developed. ECAE, therefore, has a potential to emerge as an important metal processing method for obtaining ultra-fine grain structures in alloys in bulk forms.…”

“…Spot welding electrodes perform three purposes: (1) to conduct welding current to the work and determine current density in the weld zone, (2) to transmit force to the workpiece, and (3) to dissipate heat from the weld thus thermally constraining the nugget. If the application of pressure were not involved, electrodes could be selected almost entirely on the basis of electrical and thermal conductivity.…”

EBSD Analysis of Deformed and Partially Recrystallized Microstructures in ECAE-Processed Copper

“…In many early publications, microstructures produced by ECAE have been described as homogeneous [1,2]. More detailed microstructure analysis however indicates that the ECAEdeformed materials are typically heterogeneous.…”