Papers by Keyword: ECAE

Abstract: Al-Mg alloys processed by Severe Plastic Deformation (SPD) have higher strength due to grain refinement by dynamic recrystallization. Generally, the relationship between grain size and strength is expressed by the Hall-Petch relationship, but the strength of Al-Mg alloys processed by SPD is higher than expected from the Hall-Petch extrapolation. This phenomenon is called ``Extra-Hardening. In this study, Al-3mass%Mg alloys processed by SPD were annealed, and the fraction of grain boundaries was measured by EBSD to determine the effect of grain boundaries on the strength. The results suggest that Extra-Hardening may be an effect of strengthening by SGB, which changes significantly with the number of passes and annealing, and constant LAGB strengthening. Strength predictions using the fraction of grain boundaries were in good agreement.

Abstract: Equal Channel Angular Extrusion (ECAE) is used as a top down process to produce bulk nano/ultrafine grain structured materials by inducing high amount of strain with less experimental set up. In the present study AA 5083 alloy with circular and square cross sections are extruded at room temperature using two dies having cannels with circular and square cross sections respectively. Both the dies used in this study are having same channel angle (Φ)120⁰ and outer corner angle (Ψ) 20⁰. The circular and square billets are extruded for four times in route B_C. The objective of this work is to study the effect of cross section of the billet, number of passes on grain refinement, mechanical properties and wear behaviour of AA 5083. Significant reduction in grain size is observed in extruded material using Field Emission Scanning Electron Microscope (FE-SEM) in the range of 80nm to 600nm after four passes. The microhardness in extruded materials is improved with no. of passes in both cross sectioned billets and it is more predominant for square billets even after two passes. The effect of dead zone is less in case of square billets and hence they have shown more structural homogeneity. The dry sliding wear tests are conducted to study the wear behaviour of the ECAEd materials. It is observed that the wear rate and coefficient of friction are reduced with number of passes in both the cases and rate of decrease is more in case of square billets.

Abstract: Microstructural evolution of AZ61 magnesium alloy was analyzed after ECAE process. This research focused on the effects of deformation temperature and extrusion passes on microstructure of AZ61 magnesium alloy. The results showed that microstructure have not improved significantly at the lower temperature. Grains can be refined greatly at deformation temperature of 370°C. With an increase of extrusion passes, grains tend to be much refined, which is beneficial to obtaining good property.

Abstract: Deformation behavior of porous aluminum alloys with aligned unidirectional pores through equal-channel angular extrusion (ECAE) was investigated. The porous aluminum alloys were fabricated by dipping pure aluminum pipes into semi-solid slurry base metal. The pipes did not detach from the base metal even through the ECAE process. Comparing the sample dimension of pores before and after ECAE process, the amount of decrease in a dimension of pores was 19.4% in this study. The Vickers hardness increased by work hardening. Especially, the hardness value of area where plastic flow arose increased significantly. These results show that we can improve the mechanical properties with maintenance of the porous structure and measure the amount of the sample deformation quantitatively.

Abstract: Severe plastic deformation (SPD) is one of the processes used to refine the microstructure of materials. Equal Channel Angular Extrusion (ECAE) is the most common method of SPD. In this study, AL-6063grain refinement was performed using the Equal Channel Angular Extrusion method. The material was extruded up to 6 passes at a temperature of 200°C following route A. A suitable die sets equipped with heating elements alongside a thermometer was employed with the intention of extruding the material. Between the two channels, there was an angle of 90^°. The results showed that the material grain average diameter decreased from 45μm to 2.8 μm after 6 passes of the ECAE. The Charpy test was used for measuring the fracture energy of various samples. The fracture toughness was the function of this energy. According to this experiment, the fracture toughness rose as the number of the ECAE process elevated. Moreover, the toughness improved for 90% after 6 passes of the ECAE process.

Abstract: The numerical simulation of equal channel angular extrusion (ECAE) with variable back pressure was researched by applying the commercial Deform-3D software, in which choosing the hard deformation materials of 7075 aluminum alloy, and comparing the traditional ECAE without back pressure process. The influence of back pressure on the mean stress and the effective strain rate in the shear deformation zone was studied. The results show that the extrusion force transformation laws were different in both load ways, with the increase of back pressure, extrusion force enhances increasingly, but the final load-time curves tended towards stability, but in ECAE without back pressure, the final load-time curves tended towards decreasing; thus the whole deformation process can be divided into different stages. In addition, the larger the absolute value of the hydrostatic stress at the corner, the more beneficial to refine grain and improve the plasticity. The back pressure makes the distribution of effective strain rate in plastic deformation area more uniform and improves the uniformity of deformation.

Abstract: A new processing procedure was applied to an Mg alloy. This procedure involves the equal channel angular extrusion (ECAE) process and laser melting surface treatment. A commercial Mg alloy was first produced by equal channel angular extrusion (ECAE) process. Then the laser melting surfave treatment was carried out after ECAE. The effects of ECAE and laser melting on tribological properties of the alloy were investigated. Experimental results showed that the mechanical properties and tribological properties of the alloy were improved after ECAE. The laser melting surface treatment can further improve the tribological properties of Mg alloy.

Abstract: A commercial Mg alloy was prepared through equal channel angular extrusion (ECAE) process. The effect of ECAE on mechanical and tribological properties of the alloy was investigated. Experimental results showed that the hardness and strength of the alloy with ECAE were higher than that of the alloy without ECAE and increased with the increase pass number. The friction coefficient and wear resistance of the alloy after ECAE were significantly improved.

Abstract: A biodegradable Mg matrix and nano β-tricalcium phosphate (β-TCP) particles reinforced composite Mg-2Zn-1Ca-1β-TCP was fabricated for biomedical applications by high shear solidification combined with equal channel angular extrusion (ECAE). Optical and electron microscopy, EBSD analysis and mechanical and electrochemical testing were carried out to characterize the microstructure, texture and mechanical and corrosion resistance of the material. The high shear solidification resulted in a fine and uniform grain structure with β-TCP particles evenly distributed in the matrix in clusters of 5-20 μm in size. The as-cast microstructure was replaced by a refined deformation microstructure after ECAE processing at 300 °C, during which the β-TCP particle clusters were largely dispersed, giving rise to the formation of a uniform dispersion of individual β-TCP particles in the matrix. The deformation processing by ECAE increased both the hardness and the corrosion resistance of the material. The dispersed individual nano β-TCP particles were considered to be an important factor responsible for the improved corrosion resistance after ECAE. Texture development during ECAE and its effect on the corrosion resistance was examined.

Abstract: Equal channel angular extrusion (ECAE) is a process used to introduce severe plastic deformations (SPD) to processed materials with the aim of improving their mechanical properties by reducing the grain size. In order to investigate the effect of die angle on stress and strain produced by ECAE, a new die was designed and the finite element analysis (FEA) was carried out to simulate the ECAE process. The new die is comprised of one internal mold, two external molds and one pressure rod. The main advantage of new die is it can be used for different die angle wihout changing the external mold. As a reult, the new die design reduces the tool cost and improve the ECAE process efficiency. The FEA results show that shear deformation occurred during ECAE, and the maximum effective strain was about 1.669 locating at bottom of the workpiece.