Equal Channel Angular Pressing Die Outer Corner Angle Influence on Flow and Strain Homogeneity

Abstract

Equal channel angular pressing (ECAP) is the most promising severe plastic deformation (SPD) technique for fabrication of bulk ultrafine grain materials, [1] compaction of powders, [1,2] and property enhancement of tubular materials. [3] The strain induced during the ECAP is mainly influenced by tool angles: channel angle 'j' and outer corner angle 'w' according to the equations developed from slip line theory [4] and geometrical approach. [5] In addition to that the friction between the die and sample, work/strain hardening of the materials, speed and temperature of the process also influence the induced strain. A number of studies were carried from last two decades, to analyze the influence of all the above parameters on deformation behavior and strain variations. The influence of channel angle on deformation behavior and strain distribution was extensively studied through realistic experiments, [6,7] finite element and physical modelings [7][8][9][10][11][12][13][14][15] for a range of channel angles. The influence of outer corner angle on deformation behavior was also widely studied through FEM, [15][16][17][18][19][20][21][22][23][24][25][26] physical modeling, [9,24,27] and realistic experiments. [26][27][28] However, most of the physical modeling and realistic experiments were limited to the effect of two outer corner angles. [9,24,27,28] In addition, a few studies do not consider the most important factors like friction and strain hardening of the material. [14,17,23,24] Hence, there is a need for an experimental study with a range of outer corner angles, along with the consideration of strain hardening of material and influence of friction, to analyze the deformation behavior, flow and strain homogeneity of the ECAP.Flow and strain homogeneity influence the mechanical properties and microstructure of the deformed materials. In order to analyze the influence of outer corner angle on deformation behavior, strain and flow homogeneity, several realistic experiments [26][27][28] were carried from last two decades. Flow homogeneity was analyzed in terms of hardness measurements after processing the samples with solid and split dies with round (w = 20°) and sharp (w = 0°) outer corners, respectively. [28] Deformation behavior and strain variations were analyzed through processing three different materials with two different outer corner angles: w = 0 and 60°. [27] Our recent study [26] showed the influence of outer corner angle on deformation behavior through finite element simulations and experiments by fabricating the different outer corner angle, w = 0, 22, 60 and 90°, dies with a fixed channel angle of j = 90°. That study showed that the outer corner angle is the cause of the inhomogeneous deformation behavior in ECAP. However, in that work very little emphasis was given on strain homogeneity. According to authors knowledge, till now no work has been published by showing the influence of outer corner angle flow and strain homogeneity for a range of outer corner angles (w = 0 to 90°) by both simulations and...

Finite element analysis of the bending behavior of a workpiece in equal channel angular pressing

“…The shear strain in the bottom region is increased due to the friction effect and is reduced due to strain hardening effect. Strain hardening also generates a corner gap between the workpiece and die, which has been widely discussed in earlier studies [3,9,13,14]. This uniform deformation along the width direction is the main reason for the lack of bending.…”

“…To fabricate the bulk ultrafine grain materials, variety of die designs with different tool angles, and different processing routes have been used [1]. The strain distribution and deformation behavior during the ECAP, which was influenced by tool angles, friction, and material behavior, was studied through finite element analysis (FEA) [9][10][11][12][13][14][15][16][17][18][19][20].…”

Effect of Deformation Homogeneity on Grain Refinement of AZ31 Magnesium Alloys Based on FEA during ECAP

“…corner. And because of the force condition of the material inside and outside the corner is inconsistent [11], the flow rate at inner corner is lower than that at outer corner. So the square gird turns into sector gird.…”

“…The research was supported by Key Fund Project of Sichuan Provincial Department of Education (NO.11ZA001), Key Laboratory of fluid and power machinery, ministry of education (SBZDPY- [11][12][13][14][15][16]) and open research fund of key laboratory of Sichuan, Xihua University (NO.SZJJ2009-018 and SZJJ2012-001).…”

Plastic Flow and Strain Homogeneity of an Equal Channel Angular Pressing Process Enhanced through Forward Extrusion

“…Recently, it was found that the strain homogeneity of the ECAP process dictates the mechanical properties of the deformed materials. 26,27) Hence, it is also necessary to understand the strain homogeneity of ECAP-FE combined processes. Thus, in the current study, the deformation flow, strain homogeneity, and load requirements of FE and ECAP combined processes of FE+ECAP and ECAP+FE are numerically investigated and compared with those values in individual FE and ECAP processes.…”