Design and Fabrication of Equal Channel Angular Extrusion Process Analysis for Non-Ferrous Materials
©2016
Textbook
52 Pages
Summary
“Equal Channel Angular Extrusion” (ECAE) is a significant method in industrial forming applications, which is the most important method for the production of ultrafine grained bulk samples, where plastic strains are introduced into the bulk material without any changes in the cross section. ECAE has different die channel angles from which an optimum die channel angle should be identified so that efficient mechanical properties will be obtained.
This study is focused on the plastic deformation behavior of Al alloys by modeling ECAE with experimental and finite element software. A solid model was generated using CATIA. The STL files of ECAE die generated in CATIA were used in DEFORM-3D for simulations. The experiments are performed by designing the ECAE tools such as die, punch and billet. A series of numerical experiments were carried out for the die angles of 115°, 125°and 135° and outer corner angle of 6°, using a billet diameter of 9mm and a height of 70mm. A detailed analysis of the strains introduced by ECAP (“Equal Channel Angular Pressing”) in a single passage through the die is noted. The experiments are conducted by attaching the ECAE tools to the Universal Testing Machine on aluminum alloy. The dimensions are followed for ECAE by taking considerations from the existing literature into account. On the basis of the experiment and simulation results, load, displacement, and punch force are evaluated and compared with each other.
This study is focused on the plastic deformation behavior of Al alloys by modeling ECAE with experimental and finite element software. A solid model was generated using CATIA. The STL files of ECAE die generated in CATIA were used in DEFORM-3D for simulations. The experiments are performed by designing the ECAE tools such as die, punch and billet. A series of numerical experiments were carried out for the die angles of 115°, 125°and 135° and outer corner angle of 6°, using a billet diameter of 9mm and a height of 70mm. A detailed analysis of the strains introduced by ECAP (“Equal Channel Angular Pressing”) in a single passage through the die is noted. The experiments are conducted by attaching the ECAE tools to the Universal Testing Machine on aluminum alloy. The dimensions are followed for ECAE by taking considerations from the existing literature into account. On the basis of the experiment and simulation results, load, displacement, and punch force are evaluated and compared with each other.
Excerpt
Table Of Contents
iv
LIST OF FIGURES
3.1
Schematic representation of ECAE setup
19
3.2
Universal Testing Machine fixtures
20
3.3
UTM Hydraulic system unit
21
3.4
Punch and different channel angles of die
23
3.5
Modeling of punch
26
3.6
Modeling of die
26
3.7
Assembly of ECAE setup
27
3.8
ECAE setup on Universal Testing Machine
28
4.1
Before and after ECAP processing of the Al samples
31
4.2
Stress formations at different progressions for die channel angle of 105°
32
4.3
Stress formations at different progressions for die channel angle of 115°
32
4.4
Stress formations at different progressions for die channel angle of 125°
33
4.5
Stress formations at different progressions for die channel angle of 135°
34
4.6
Comparison of extrusion load with displacement with die channel angle
of 105°
34
4.7
Comparison of extrusion load with displacement with die channel angle
of 115°
35
4.8
Comparison of extrusion load with displacement with die channel angle
of 125°
35
4.9
Comparison of extrusion load with displacement with die channel angle
of 135°
36
v
LIST OF TABLES
3.1
Tool dimensions and processing parameters
22
3.2
Material properties of the aluminum
28
4.1
Die channel angles and their obtained results
37
1
CHAPTER 1
INTRODUCTION
Equal channel angular extrusion (ECAE) is a technique for producing ultra fine grain
structures in submicron level by introducing a large amount of shear strain into the materials
without changing the billet shape or dimensions. Ultra-fine grained (UFG) materials, having
grain sizes in the sub-micrometer range, have always been the focus of interest and extensive
research in materials science. Conventional heavy deformation techniques such as drawing
and cold rolling are also accompanied with significant refinement in the microstructure. The
most important reasons for this interest and corresponding research activities are the unusual
mechanical and physical properties that UFG materials possess, when compared to
traditionally produce coarse-grained materials. This interest has grown significantly in the
recent years with the development of several plastic deformation (SPD) methods. Which
provides the opportunity to produce bulk UFG materials without difficulties encountered
during the previous fabrication methods. Equal channel angular extrusion (ECAE) is one of
the most promising methods in SPD methods, since the workpiece cross section does not
change during the process. The details of ECAE are discussed in the following sections.
1.1 History of Equal Channel Angular Extrusion Process
The equal channel angular extrusion (ECAE) was developed by Segal in 1981. Now the
process is extensively used to achieve ultra-fine grained structures in bulk form, which gives
rise to attain the outstanding properties such as high strength, toughness and hardness at
ambient temperatures, exhibition of superplastic behavior at high strain rates at elevated
temperatures.
In ECAE process, two channels of the same cross section intersect at a certain angle
to form the die. The billet either round or square cross section, is pushed from the top into
this die by means of a flat faced ram and is subjected to simple shear without any change in
cross sectional dimensions. By repeated pressings, the work piece can attain very large strains
which are almost impossible to obtain via conventional manufacturing methods.
Equal channel angular extrusion processed parts can be used in industrial applications,
aerospace and automotive industries, the products include fasteners like screws, screw rivets
used in the assembly of aluminum components for aircraft and other structures, elements for
aircraft fuselages (stringers, skin plates, etc) etc.
2
Equal channel angular extrusion is also strain hardening process. Strain hardening
(also called work hardening or cold working) is the process of an increasing stress; stress is
required to produce plastic deformation and the metal apparently becomes stronger and more
difficult to deform. When a metal is plastically deformed, dislocations move and additional
dislocations are generated. The more dislocations within a material, they will interact more
and become pinned and tangled. This will result in a decrease in the mobility of the
dislocations and a strengthening of the material. This type of strengthening is commonly
called cold-working. It is called cold-working because the plastic deformation must occur at a
temperature low enough that atoms cannot rearrange themselves. When a metal is worked at
higher temperatures (hot-working) the dislocations can rearrange and little strengthening is
achieved.
Equal channel angular extrusion is extensively used in the bulk metal forming under
compressive conditions, without altering the shape or dimensions of the billet. The
formability of bulk material during ECAE process depends on the parameters like lubrication,
punch force, die inner corner angle and outer corner angle, die-punch clearance, in addition to
mechanical properties and shape of the billet and parts geometry. The proper selection of
these variables helps to reduce the defects in the ECAE process. It also helps to implement
the optimum results and improves the mechanical properties of the materials used in the
process.
When it comes to material processing for industrial and research applications, the
light metals will have a great amount of interest. The property of lightness translates directly
to the material property enhancement for many products since by far the greatest weight
reduction is achieved by a decrease in density. The term "light metals" has traditionally been
given to aluminum because they are frequently used to reduce the weight of components and
structures. This is quite expected since specific strength becomes one of the most important
desired properties and is easier to be achieved due to the low densities of such materials.
1.2 Aim and Scope of the Study
In this study, the effects of equal channel angular extrusion process parameters investigated
by both experimentally and numerically. The study is initiated by modeling ECAE tools.
ECAE process parameters namely different die channel angles, outer corner angle; numbers
of passes, punch force are studied. The experiments are carried out with the help of universal
testing machine by fixing the ECAE tools setup. The simulations are performed in finite
element code by importing the tool into FE code. The dimensions of the ECAE tool, the size
3
of the billet, properties of material, the varied process parameters and power law criteria
considered for simulations are given in Chapter 3 elaborately. From the simulations die
channel angles, punch force, load, displacement are evaluated for all conditions. From the
overall analysis of the results, optimizations of the ECAE process parameters for different die
channel angles are suggested and produce maximum property improvement.
1.3 Equipment Used
The equipment on the basis of the type of force used to drive the punch is classified as
follows:
1.3.1 Hydraulic Press
In this type of equipment the force required to derive the ram (punch) is supplied by
hydraulic means to deform the metal plastically
1.3.2 Mechanical Press
In this type of equipment the force required to derive the ram (punch) is supplied by
mechanical means to deform the metal plastically.
1.4 Tasks Involved
· Design, Modeling and Fabrication of whole laboratory level ECAE process setup.
· Perform the ECAE process simulations using DEFORM 3D a finite element code.
· Conduct the ECAE process experimentation on universal testing machine.
· Investigate the effect of different die angles on ECAE process.
· Obtain the forming behavior of aluminum 1100 material at different die angles
115°, 125° and 135°.
· Compare and validate Experimental results and simulation results.
· Optimize die channel angles to obtain ultrafine grain structure and improving
mechanical properties of the aluminum alloy.
1.5 Organization of the Study
The study is divided into five chapters. In the first chapter, general information about the
equal channel angular extrusion process and outline of the present study is given. The next
chapter is the literature review, in which previous studies on equal channel angular extrusion
4
process, experimental results, numerical simulations and the analysis are summarized. The
finite element analysis and experimental applications of the ECAE process are overviewed.
In the third chapter the factors influencing the equal channel angular extrusion process, the
effect of various process parameters of the ECAE process, the use of finite element analysis
for numerical simulations and experimental investigations are explained. Fourth chapter
focused on representation of the results obtained by varying the process parameters. The fifth
chapter deals with the conclusion of the ECAE of aluminum with different die angles.
5
CHAPTER 2
LITERATURE SURVEY
In this chapter, a few research papers have been indicated related to present work objective.
The investigations provided the vast amount of information about the Equal channel angular
extrusion process. From the various studies, they suggested many approaches on ECAP. In
this section, a survey on experimental works, numerical simulations and finite element
analysis of equal channel angular extrusion process has carried out.
2.1 Experimental Studies on Equal Channel Angular Extrusion Process
From a decade, there were many studies carried out on experimental observations on ECAP
and various parameters involved in the process. For example, Segal et al (1999) studied
about the plastic flow during the one step and evolution of shear planes during multi pass
extrusion. In this work, pure aluminum was processed through equal channel angular
extrusion with low friction and tool angle of 90°. The results found that the equivalent strains
cannot be unique between ECAE and ordinary forming operations. Each pass of ECAE
process was developed thin shear bands along the channels. Segal (2003) investigated about
the equal channel angular extrusion by slip line method. In this analysis, it is noted that
contact friction was important effect on stress-strain state during ECAE. When the friction
increases from zero to maximum, the strain distribution remains uniform and effective strains
reduced. Wei et al (2003) studied about the microstructure and mechanical properties of
tantalum after equal channel angular extrusion process with four passes. After completing the
ECAE processed material was tested for under quasi-static and dynamic loading conditions.
The result found that, the tantalum shows perfectly plastic behavior under quasi-static loading
without strain hardening. In dynamic loading condition, slight softening due to adiabatic
heating. Markushev et al (2004) studied about the structure and mechanical properties of
commercial Al-Mg 1560 alloy after equal-channel angular extrusion. The sub
microcrystalline deformation structure has obtained by ECAE and it was transformed into
sub-micron and microcrystalline grain structure upon annealing. The nature of
recrystallization and phase transformation processes were discussed. Mechanical properties
such as strength, hardness, ductility and crack resistance of the alloy were demonstrated. The
result showed that ductility and crack resistance were decreased with transformation of the
SMC structure. Wang et al (2004) studied about the effect of deformation temperature on the
microstructure developed in commercial purity aluminum by equal channel angular extrusion
6
process. The authors have demonstrated the effect of temperature on the microstructures was
investigated after ECAE. They characterized the micro structural parameters, including grain
size, shape and boundary misorientation. It is noted as sub grain size was increased due to
increase the temperatures from 289-523K.
Saravanan et al (2006) studied about the equal channel angular pressing of pure
aluminum to produce ultra-fine grain structures in submicron level. The ECAP technique was
attempted to 99.5% pure aluminum. The aluminum alloy was characterized by optical
metallography, atomic force microscopy and hardness measurement. The result found that,
the number of passes important, to achieve a homogeneous microstructure in pure Al. The
ultimate equilibrium grain size was obtained through ECAE process. Fang et al (2006)
studied about the effect of equal channel angular pressing on tensile properties and fracture
modes of casting Al-Cu alloys. In this work the grains of the two alloys refined to submicron
level after four passes of ECAP. The result found that, the tensile fracture strength and static
toughness was increased with ECAP pass. The failure modes of two Al-Cu alloys were
exhibit different features, such as necking degree decreases and shear feature becomes more
with increasing of ECAP. Gazder et al (2006) studied about the progressive texture evolution
during equal channel angular extrusion process. The progressive texture evolution was seen
during second pass of equal channel angular extrusion of copper. In this work, the uniform
texture predictions were achieved by visco-plastic self-consistent. This process was using
finite element predicted deformation. The result found from above work, the greatest texture
changes were occurred in the billet. It was found in a narrow region between the ends of the
entry channel and die intersection plane. Nagashekar et al (2006) studied the ECAP on
tubular aluminum alloy specimens. The experimental test was conducted to measure the
pressure and the mechanical properties of the extruded material. In this work, low extrusion
pressures during ECAE of tubular specimens are due to the movement of the mandrel along
with the specimen. During this work the tensile strength, yield strength, and hardness were
improved and elongation to failure was decreased. Finally this technique was improved
properties of the tubular specimen.
Yeung et al (2007) studied about the equal channel angular extrusion of high purity
gold. In this work, the high purity gold billet of 10mm diameter and it was processed up to 9
passes. The result found that, the hardness of the gold sample was increased from 30HV to 82
HV. The electron backscatter diffraction was showed an average grain size 140nm in the
extruded material. The high volume of high angled grain boundaries was determined in the
extruded gold solid. Suzuki et al (2008) studied about the equal channel angular extrusion
7
process of lotus-type porous copper. This work was investigated using ECAE die with
different die angles. The copper rod was densified by the uniaxial compression in the entry of
the channel. The pores were thinned elongated by shearing at the corner of the die. The result
found for this analysis was, due to the shear flow stress reducing the normal stress. The pore
morphology was controlled by the extrusion process. The Vickers hardness increased through
the ECAE process and improved the mechanical properties of porous metals. Paydar et al
(2008) studied about the consolidation of Al particles through forward extrusion-equal
channel angular pressing. In this work two processes were conducted in a single die, such as
forward extrusion and equal channel angular pressing. The forward extrusion-ECAP was
superior to conventional forward extrusion. This work was to achieve full density and good
bonding in entire volume of the consolidated particles. The result of this FE-ECAP process,
the bulk material has high strength and excellent ductility. The advantage of this method was
possibility of performing two processes in a single die and producing a long bar samples with
full density. Gao et al (2008) studied about the microstructure and dry sliding wear behavior
of Cu-10%Al-4%Fe alloy produced by equal channel angular extrusion process. The
aluminum bronze alloy was processed by ECAE at higher temperature. Authors were
investigated the effect of microstructure, mechanical and tribological properties of the alloy
was investigated. The result found, the grains were refined and grain size was decreased after
ECAE. The friction coefficient of the specimen was decreased with decreasing of grain size.
The grain refinement can improved wear resistance and the load bearing capacity of the alloy
during dry sliding. Hardness and strength of the alloy was increased due to increase the
ECAE passes.
Daly et al (2009) studied about the effect of annealing on the microstructure and
properties used equal channel angular extrusion. In this work, 99.99 wt. % of the pure copper
was processed at room temperature. The ECAE technique was processed in the material,
without changing the sample dimensions through ECAE process. In this work, the micro
structure and micro hardness were studied. The result found that, increased annealing
temperature, the microstructure has becomes more homogeneous while the micro hardness
become decreased. Atef Rebhi et al (2009) studied about the characterization of aluminum
processed by equal channel angular extrusion: effect of processing route. In this work, an
aluminum alloy was processed by ECAE via routes B
c
and C up to four passes. This process
was characterized the evolution of the microstructure and changes of mechanical properties.
The result of this work was the tensile test showed; the routes B
c
and C lead to higher flow
stress and lower strain-hardening coefficient after ECAE. The dynamic recovery was more
8
effective in route C than route B
c
due to high density of dislocations. Chinh et al (2010)
studied about the processing of Age-hardenable alloys by an equal channel angular pressing
at room temperature. In this work, the microstructure, strength, and ductility of age
hardenable Al Zn Mg alloys was investigated. The investigation was reported, a critical
strategy for the processing of age-hardenable alloys by conducting the quenching. The result
of this work was improving the strength, reduced the possibility of the formation of micro-
cracks during several plastic deformations by using ECAP. Further, the application of ECAP
process may increase not only the strength but also the ductility of the age-hardenable
samples after a certain number of ECAP process. Biswas et al (2010) studied about the room-
temperature equal channel angular extrusion of pure magnesium. This work was conducted at
room temperature, to produce ultrafine grain size through ECAE. The method of this analysis
was, to achieve required grain sizes had proposed. It was to obtain suitable initial orientation
with high Schimed factor for basal slip. To take advantage of low stacking fault energy of
basal and high stacking fault energies of prismatic plane. The temperature deformation was
lower in steps, leading to continual refinement of grains. The result of this work was the
hardness of the material increased with decrease in the grain size according to hall-pitch
relationship.
Vasile Danut et al (2010) studied about the mechanical behavior comparison between
unprocessed and ECAP processed 6063-T835 aluminum alloy. The ECAE method was used
to modify the microstructure and producing ultra-fine grained metals and nano materials.
This work was to investigate the mechanical behavior of the ECAP processed material by
uniaxial tensile test. This work was the ultimate tensile strength, yield strength, and strength
to fracture was observed after ECAP. The result of the work was found, the ECAP process
was to increase the mechanical properties. Dong-Hwan et al (2010) studied about the
mechanical behavior and micro structural evolution of commercially pure titanium. The T-
type ECAP apparatus was developed to improved the efficiency of common ECAP and the
finished products. CP-Ti billet was much stronger; it was produced by using the ECAP
process. The result of this work was decreased the grain size occurring through the multi pass
ECAP caused by SPD. In this process spatial variations of microstructure together with
relevant mechanical properties were predictable. The material status in the plastic forming
process coupled with the processing condition and particularly focused to determine the
properties of finished products. Orlov et al (2011) studied about the mechanical properties of
magnesium alloy ZK60 by combines conventional extrusion and equal channel angular
pressing. In this work, only single pass process of ECAE was done. The result of this work
Details
- Pages
- Type of Edition
- Erstausgabe
- Year
- 2016
- ISBN (PDF)
- 9783960676065
- ISBN (Softcover)
- 9783960671060
- File size
- 3.3 MB
- Language
- English
- Publication date
- 2016 (November)
- Keywords
- ECAE Industrial application Forming process Die channel Plastic deformation Aluminium alloy Equal Channel Angular Extrusion ECAP Equal Channel Angular Pressing
