Hardness and Texture of Electrolytic Copper Processed by ECAP at Ambient and Warm Temperature

Among several severe plastic deformation (SPD) methods, the Equal Channel Angular Pressing (ECAP) process is one of the most popular. This process's main characteristic is producing materials with ultra-fine or nanometric grains. Due to these microstructural changes, it is possible to improve mechanical properties such as strength and ductility. In this perspective, the aim of the present work was to evaluate the variations of the mechanical hardness property associated with microstructural and textural changes of pure copper as a function of its processing by SPD via ECAP. For this, the material was submitted to four passes through routes A (the sample is repetitively pressed without any rotation between each pass) and Bc (the sample is rotated in the same sense by 90° between each pass) at cold and warm temperatures. Through the obtained result, it was verified that the ambient temperature of the Bc route was the one that promoted greater homogeneity in the microstructure and weakening of the texture after the fourth pass. On the other hand, warm processing of copper by ECAP promoted a softening of the samples and a homogeneous distribution of hardness in both routes.

Microstructural Evolution, Hardness, and Strengthening Mechanisms in SLM AlSi10Mg Alloy Subjected to Equal-Channel Angular Pressing (ECAP)

The AlSi10Mg alloy is characterized by a high strength-to-weight ratio, good formability, and satisfying corrosion resistance; thus, it is very often used in automotive and aerospace applications. However, the main limitation of using this alloy is its low yield strength and ductility. The equal-channel angular pressing is a processing tool that allows one to obtain ultrafine-grained or nanomaterials, with exceptional mechanical and physical properties. The purpose of the paper was to analyze the influence of the ECAP process on the structure and hardness of the AlSi10Mg alloy, obtained by the selective laser melting process. Four types of samples were examined: as-fabricated, heat-treated, and subjected to one and two ECAP passes. The microstructure analysis was performed using light and electron microscope systems (scanning electron microscope and transmission electron microscope). To evaluate the effect of ECAP on the mechanical properties, hardness measurements were performed. We found that the samples that underwent the ECAP process were characterized by a higher hardness than the heat-treated sample. It was also found that the ECAP processing promoted the formation of structures with semicircular patterns and multiple melt pool boundaries with a mean grain size of 0.24 μm.

Analysis of processing variables in Equiangular Channel Press deformations

Equiangular Channel Pressing (ECAP) is by far the most promising technique, by the severe plastic deformation (SPD) method, being able to produce large volumes of materials sufficient for practical applications. The ECAP process can be repeated until refining saturation is reached, leading to large amounts of shear strain. The reason behind the exceptional properties obtained in materials processed by ECAP was attributed to the microstructure of the material obtained in this deformation process. This work investigated the ECAP strain variables in the literature in order to analyze the effect of each of these on the microstructure of processed materials. The articles were collected from the following databases: ScienceDirect and the Scientific Electronic Library Online (SciELO) electronic library, as they include national and international literature. Based on the results found, it could be seen that several parameters must be analyzed to deform pure metals and alloys, to refine the microstructure, such as bending angle and channel angle of the strain matrix, number of passes, and pressing temperature. It was possible to verify that changes in these variables configure changes in the microstructure.

Microstructure and Strain Hardening Behaviour of Iron Chromium Alloy Subjected by Severe Plastic Deformation

Microstructure and strain hardening behaviour of iron-chromium alloy subjected to severe plastic deformation (SPD) have been investigated in grain refinement and deformation routes. Equal channel angular pressing (ECAP) was used in this SPD technique due to their un-change dimension billet. The purpose of this research is to investigate the structure and the strain hardening of iron chromium alloy subjected by ECAP process. The ECAP process was carried by routes A, Bc and C up to four passes at 423 K temperature. The strength of the material was measured by tensile testing with 3 mm gauge length, and the strain hardening behaviour was investigated based on the true stress-strain curve. The effect of the deformation route on microstructure and texture was observed by electron backscattered diffraction (EBSD) analysis at the normal, transverse and rolling direction. The result showed that route Bc showed the highest strength and ductility of the ECAP processed material compare to other routes due to their 90 degrees rotation of each ECAP passes number. The increased strength of materials was also associated with grain refinement and accumulation dislocation. It concluded that the ECAP process by route Bc could be used for further material treatment and application for industrial purposes.

Effect of Preliminary Deformation on Microstructure and Texture of Iron-Chromium Alloy Prepared by Severe Plastic Deformation

The effect of preliminary deformation on the microstructure and texture of iron-chromium alloy prepared by severe plastic deformation (SPD) has been investigated in grain refinement and inhomogeneity structure. Equal channel angular pressing (ECAP) is a well-known SPD process that uses a die channel with a sharp angle. The texture and misorientation map of ECAP processed material was observed electron backscattered diffraction (EBSD) analysis, providing information on structure evolution. The observation was done in the transverse plane from the middle to the sub-surface. The data logger also records the pressure of the ECAP process. The result showed that the sub-surface has a more deformed structure than the middle due to the die channel's sharp angle and shear direction. The texture exhibited a random orientation after the first pass ECAP process. The stacking fault energy and accumulation dislocation are also associated with this process. Several shear bands can be seen clearly, which is parallel to the shear direction. It concluded that the preliminary deformation by ECAP was effective to promote grain refinement due to their high equivalent strain

Microstructure Evolution of AS41 Magnesium Alloy in ECAP

ECAP is a continuous multi-pass extrusion process that enables the specimen to obtain considerable cumulative deformation to refine the grain. In this paper, ECAP was used to deform AS41 magnesium alloy at 350°C, and the microstructure was observed and analyzed. The results show that the ECAP process has excellent effect on grain refinement and uniform microstructure. The grain size of AS41 decreases from 200μm to 20μm, and the microstructure is more uniform than that of as-cast sample. The reason is that the original grain is broken and refined under the action of shear force, and dynamic recrystallization occurs at the same time, resulting in small recrystallized grains. The Mg2Si particles were redistributed during ECAP and uniformly distributed in the crystal in rod shape.

Influence of the ECAP Tool Channel Geometry on the Structure and Properties of Al-3%Mg Aluminium Alloy

In this study, commercial Al-3%Mg aluminium alloy was subjected to ECAP processing using two different ECAP die configurations. The first one – conventional and the second one modified in which a part of the exit channel in the ECAP die, causes twist deformation, to impose extra shear strains to the sample. The local changes in microstructure were characterized by Light Microscopy, SEM equipped with an EBSD facility and TEM. Mechanical properties of the ECAP processed samples were compared based on hardness measurement. The results showed that when ECAP with modified die, the greater grain and crystalline refinement is possible. The microstructures exhibit high dislocation density within subgrains with non-equilibrium and Moiré boundaries. Moreover, the mechanical examinations display a significant improvement in hardness and calculated yield strength when the ECAP process is conducted using a modified die.

Effect of ECAP Die Angle on Mechanical Properties and Biocompatibility of SS316L

In this study, ultrafine grain (UFG) SS316L was produced using an equal channel angular pressing (ECAP) process at two different die angles namely 120° and 126°. The effect of different die angles on mechanical, corrosion, and surface properties were thoroughly investigated. Furthermore, the subsequent effect on the cytotoxicity of SS316L was investigated. The microstructure observation shows ECAP processing has produced an elongated, finer grain size at 120° than 126°. The ECAP processing also increases the hardness of SS316L. There is no change in wettability and surface roughness observed. However, the ectrochemical measurement reveals that ECAP processing improves the corrosion resistance of SS316L. The cytocompatibility of ECAPed SS316L was evaluated by both a direct and an extract methods, finding the contribution of grain refinement by ECAP processing.