bluuebunny/crossref_metadata_2025 huggingface dataset:
FE Simulation of Complex Contour Forming of Sheet Metals Based on Laser Bending
Authors: Chen Yi Bin , Zhou Jian Zhong , Huang Shu , Sun Yue Qing
Published: March 2009

Laser bending is a flexible forming process which forms sheet metal by means of stresses
induced by external heat instead of external forces. In this paper, a three-dimensional coupled
thermal-mechanical model for numerical simulation is established with finite element code
ABAQUS. Some key problems about the simulation of laser bending are investigated in detail, and
the reasonable solutions are presented. Taking AISI-1008 steel as an example, numerical
simulations are carried out for the complex contour forming of sheet by using Sequentially Coupled
Thermal-Stress Analysis technique. Then the corresponding experiments are performed to validate
the simulation results. Good correlation between the numerical simulation and the experimental
results was demonstrated.
Quality Measure and Control System for the Whole Process of Arc Welding
Authors: Li Zhi Yong , Wang Bao , Ding Jing Bin
Published: March 2009

Welding quality control is critical for welding manufacturing. However, the factors that
affect welding quality exist in the whole welding process. Whole process welding quality control is
a technology control process that can control the welding quality from choice of the welding
material, stability of the welding process and quality assurance after welding. In this paper, a quality
measure and control system is developed. The system is consisted of three modules: Technology
property evaluation and welding material choice module is based on Analysator Hannover. This
module can evaluate three type of welding material: electrode, solid welding wire and flux-cored
wire. The welding process stability evaluation module can collect electrical and light spectral signal
for disturbance factors diagnosis during the welding. The metallurgical structure and property
forecasting module call the CCT diagram data base for predicting he metallurgical structure and
mechanical property of the weld affected zone and weld metal. For stainless steel, a predicting
method based on Schaeffer is also provided in this module.
Research on One New Type of Rapid Prototyping Based on Laser-Induced Chemical Liquid Deposition
Authors: Song Dan Lu , Zhao Deng Feng , Chen Kui Ru , Yao Xiao Peng , Chen Wei Chuang
Published: March 2009

Based on introducing Laser-induced Chemical Liquid Deposition (LCLD) technology,
this paper gave a new type of RP system graph based on the technology, and it has introduced the
work process of this system on detail. The process of LCLD is controlled by thermal transfer if the
heights of liquid and metallic material are changeless. Modeling thermodynamics of the part of
facular laser beam of the process of LCLD, calculating and emulating by engineering analytical
software, these researches can lead to the conclusion that the highest temperature of plating liquid
can be found if the diameter of the facular laser beam is unchangeable. The relation between
temperature and power of laser is linear on the whole. The locomotory speed of the laser beam does
little influence on temperature of plating liquid; the thermal area of plating liquid influenced by
laser is very small; the temperature in the thermal area is asymmetrical. The width of metal line of
the deposition can be controlled at a certain extent by controlling the initial temperature of plating
liquid and power of laser.
Simplified Heat Model of the Weaving Welding Processes
Authors: Yang Jian Guo , Gao Jia Shuang , Fang Hong Yuan , Zhou Guang Tao , Hu Jun Feng
Published: March 2009

Considering the specialty of the welding with weaving during the manufacturing process
of the thick plate welding structure, a coordinate transformation method is put forward to simulate
this process. The results indicate that the arc weaving process leads to the increasing temperature
gradient in the regions near the weld bead, which also raises the peak values of transverse residual
stresses. Combining the characteristic of the welding with weaving and the conversation of energy
law, simplified banding heat source models are developed.
Analysis of Arc Welded Thin-Walled Cylinders to Investigate the Effects of Welding Process Parameters on Residual Stresses
Authors: Malik Afzaal M. , Qureshi Ejaz M. , Dar Naeem Ullah
Published: March 2009

The research work presents a computational methodology based on three-dimensional
finite element model to simulate the gas tungsten arc welding (GTAW) of thin-walled cylinders.
The aim was to study the effects of two basic welding parameters (welding speed and welding
current) on weld induced residual stresses. The complex phenomenon of arc welding was
numerically solved by sequentially coupled transient, non-linear thermo-mechanical analysis. The
accuracy of the numerical model was validated through experiments for temperature distribution
and residual stresses. The results reveals that the present simulation strategy can be used as a proper
tool to get the optimized welding process parameters and minimize the in service failures of thinwalled
structures due to residual stresses.
Overview of Modeling Strength Evolution during Friction Stir Welding
Authors: Cho Jae Hyung , Kim Hyung Wuk , Kang Suk Bong
Published: March 2009

Using two-dimensional Eulerian formulations coupling viscoplastic flow and heat transfer,
the behaviors of aluminum alloys and stainless steel during FSW were overviewed. The plastic
behaviors of the materials are complicated and the flow stresses are depending on deformation rate,
temperature and deformation histories. Constitutive equations considering both strain hardening from
accumulation of crystal defects and softening from recovery or recrystallization were used to model
the materials. Strain hardening is incorporated with a strength that evolves with deformation rate and
temperature along streamlines in the flow field. Strength evolutions have a Voce-like saturation limit
because of the severe plastic deformation during FSW process. The model equations for kinematic
and temperature were solved using the standard finite element method. The evolution equation for the
strength is integrated along streamlines. The strength and temperature distribution vary with process
conditions and constitutive equations. Stainless steel and AA6061 have different strengthening
mechanisms. Modified constitutive equations were applied to reflect microstructural features of each
material.
Numerical Study on Mold Filling Process of Casting
Authors: Pan Xiao Qiang , Sun Hong Zhu , Chen Jun Da , Zhu Yu Ling
Published: March 2009

Techniques of numerical simulation on mold filling process of casting are investigated in
this paper. The mathematical model is formed on the ground of some selected theories in
computational fluid dynamics (CFD), Numerical Heat Transfer (NHT) and computational methods
to interfacial tracking. The discrete solution to the governing equations appeals to Finite Volume
Method (FVM) on structured mesh. As for viscous turbulence flow and multiphase fluid flow in
mold filling, engineering turbulence model and Volume of Fluid (VOF) method are adopted in the
algorithms, respectively. As a debut, the general-purpose CFD software is used to establish the
practicable mechanical model for the simulation. By means of numerical simulation, variation and
distribution of velocity, temperature, stress and configuration of casting, etc. with respect to time
and space in the filling process can be quantitatively analysed in detail, which is helpful for
engineers to optimize their design of technics with less time and less cost and is meaningful to
provide the subsequent simulation, solidification process of casting, with initial conditions.
Mullite Interlayer of C/Si-C-N Composites Fabricated by PIP
Authors: Lu Guo Feng , Qiao Sheng Ru , Hou Jun Tao , Gong Man Feng
Published: March 2009

Mullite interlayer of the carbon fiber reinforced Si-C-N matrix composite (C/Si-C-N)
was fabricated by liquid precursor impregnation and pyrolysis (PIP). The mixture of aluminium secbutoxide
(A1OBu) and tetraethoxysilicate (TEOS) were used as starting materials. The monophase
polymer gel used as mullite precursor could be formed from the mixture in the semi-closed air. A
mullite interlayer with a thickness about 500nm is obtained at 850°C- 1200°C. The fiber/interlayer
bonds are tight. The carbon fibers are not damaged in the fabrication procedure.
Numerical Simulation of Thermal Stress Fields during Gas Quenching
Authors: Li Zi Liang , Cheng He Ming , Chen Jun Ruo , Liu Mei Hong
Published: March 2009

In this paper, based on the analysis of coupled action of temperature, phase
transformation and stress, the phase transformation condition and equation related to the thermal
physical properties are discussed, and the transient temperature distribution of a Cr12 steel cylinder
workpiece during gas quenching was obtained by solving the governing equations with a nonlinear
boundary. According to the theories of thermal non-elasticity, computational mechanics and phase
transformation, a new constitutive equation considering effects of phase transformation with a
nonlinear surface heat transfer coefficient is proposed and is solved by means of finite element
method (FEM). The thermal stress field is obtained and a way of simulating the technology of the
heat treatment by computer is explored.
Plastic Behavior of Metals in Reverse Straining after Large Pre-Strains
Authors: Beyerlein Irene J.
Published: March 2009

The present work examines the reversal response of a face-centered cubic (fcc)
polycrystalline metal after large pre-strains. While reversal responses among different fcc metals
are similar after small pre-strains, they can vary widely after large pre-strains depending on material
and microstructure. In this article, these characteristics are considered to be governed by three
distinct mechanisms: (1) reverse glide of dislocations previously held by backstresses, (2) reverse
glide of dislocations previously held by barriers, and (3) ‘reverse hardening’ by reverse glide over
stable dislocation barriers formed in pre-straining. These small-scale mechanisms are incorporated
into a polycrystal code to investigate their influence on the macroscopic reversal response and to
interpret large strain reversal tests in the literature. It is shown that mechanism (2) is responsible
for worksoftening and reductions in hardening rate and mechanism (3) for the overshoot seen in α-
brass and other low stacking fault energy alloys. Mechanism (1) is responsible for the Bauschinger
effect and occurs in all metals. A large fraction of second phases leads to a strong Bauschinger
effect that can either reduce or postpone the effects of mechanisms (2) and (3).
Thermal Resistance Control of an Optical Module Packaging by a Heat Sink of High Thermal Conductivity
Authors: Oh Seung Hun , Kim Chang Seok , Rho Byung Sup , Jung Seung Boo , Jeong Myung Yong
Published: March 2009

In an optical module with high density and small size, it is important to maintain the
operating temperature by adequate heat dissipation. The thermal simulation of an optical module for
communication has been performed to reduce the operating temperature. To improve the behavior
of heat dissipation, we have simulated heat path and heat resistance using commercial code,
COMSOL. We have chosen simulation parameters, which include thickness, thermal conductivity,
interface area and surface roughness of heat sink and submount as an element of heat resistance. To
reduce heat resistance, it was desirable to use the material of higher thermal conductivity, single
crystalline silver, and to control the surface roughness of the interfaces. We could lower the
operating temperature of an optical module about 18 degrees by controlling the above parameters.
Bending Fatigue Characteristic of Sn-3.5Ag Solder Bump on Ni-UBM
Authors: Kang K.I. , Jung J.P. , Bang Woong Ho , Park J.H. , Oh Kyu Hwan
Published: March 2009

Bending fatigue behavior of eutectic Sn-3.5Ag solder bump bonded on FR4-PCB was
characterized by experimental and finite element method (FEM). To investigate an effect of stress
state on bump failure, which had not been weighed in conventional Coffin-Manson model of
Nf=K ⋅εp
-1~-2, ‘fatigue frequency variable’ and ‘bump viscoplasticity’ were included in analysis
procedure. As experimental results, with increasing fatigue cycles from 3,000 to 10,000, bond
strength decreased from 98.9% to 76.5%, and from 97.5% to 67.1% at the fatigue frequencies of
2.5Hz and 5.0Hz, respectively. Stress state could be critical components to determine fatigue life,
which should be combined in Coffin-Manson criteria. FEM calculation showed that higher bending
frequency led to higher normal stress development at the solder and IMC interface, but smaller plastic
strain in bump. However, bending fatigue experiment revealed discrepant results from that of
Coffin-Manson criteria. Higher bending frequency, which was predicted to give rise to smaller εp at
solder, showed dramatic bond deterioration of solder bump on UBM (under bump metallurgy). This
was confirmed experimentally through SEM (scanning electron microscopy) observation as cracks
were found at the solder bump and UBM interfacial IMC, Ni3Sn4, in case of the higher bending
frequency.
Grain Refinement of Titanium Weld by Heterogeneous Nucleation
Authors: Terasaki Hidenori , Komizo Yuichi , Nishino Fumihiro , Ikeda Masahiko
Published: March 2009

Microstructure formation of CP-Ti and TiB reinforced titanium were in-situ observed
during the thermal cycle simulated for Tungsten Inert Gas (TIG) welding, by using laser scanning
confocal microscopy. Under the in-situ observation of TiB reinforced titanium, heterogeneous
nucleation of α-phase at inclusion was clearly detected and plate growth was shown in high timeresolution.
Furthermore, it was observed that grain boundary of β -phase was pinned by the
inclusions. Microstructure difference between pure and TiB reinforced titanium was explained
based on those in-situ observations.
Small-Scale Resistance Welding of Crossed TiNi Fine Wire
Authors: Fukumoto Shinji , Morikawa Shigeru , Yamamoto Atsushi
Published: March 2009

Resistance microwelding of fine crossed wires is of increasing industrial importance for medical
devices, but the understanding of the process is very limited. A study has been carried on the
feasibility of small-scale resistance welding of crossed TiNi fine wire. Welding mechanism is
similar to that of small-scale resistance welding of crossed Ni wire, which is mainly four stages
(wire cold deformation, surface melting, molten phase squeeze-out and, solid-state bonding). The
optimum microstructure and welding parameters were proposed.
Effects of Isothermal Aging on the Microstructure and Tensile Behavior of Sn-3.0Ag-0.5Cu-0.2Co Solder
Authors: Cheng Fang Jie , Nishikawa Hiroshi , Takemoto Tadashi
Published: March 2009

Effects of isothermal aging on the microstructure and tensile behavior of
Sn-3.0Ag-0.5Cu-0.2Co (SAC305-0.2Co) solder was explored, and compared with the standard
Sn-3.0Ag-0.5Cu (SAC305) solder. The addition of Co resulted in the formation of CoSn2 phase in
SAC305-0.2Co solder matrix. The isothermal aging treatment induced microstructural coarsening
for both solders. With aging, the eutectic network has been translated into block or granular shape
particles. Meanwhile, the outline of the primary Sn phase became less distinct. The tensile test
results indicated, under as cast condition, the Co had little effect on the ultimate tensile strength
(UTS) of SAC305-0.2Co solder, whereas it suppressed the ductility. After aging, the UTS of
SAC305 was obviously decreased, whereas the elongation hardly changed. For the SAC305-0.2Co,
the tensile behavior showed two trends: one was the decrease of the UTS, which was similar to that
of SAC305; the other was the notable increase of elongation. The examination of the fracture
surfaces indicated that isothermal aging could alter the fracture pattern of SAC305-0.2Co solder
from brittle to ductile.
Numerical Modeling of Welding Arc with Complex System between Arc Plasma and Molten Electrode
Authors: Yamamoto Kentaro , Tanaka Manabu , Shinichi Tashiro , Nakata Kazuhiro , Suzuki Keiichi , Yamazaki Kei
Published: March 2009

It is important to consider the interaction between arc plasma and electrodes because
melting of electrodes strongly affects arc plasma. Therefore, a GMA model will be developed,
based on the unified model of TIG arc. As a first step, a TIG arc model with a calculation for
molten cathode shape has been proposed. This model is calculated in two cases; molten W cathode
and Calculation result of W cathode. In the case of W cathode, cathode shape change was found to
affect the arc plasma property strongly. Calculated results of radial temperature distributions on
electrode surface and arc pressure distributions at the anode surface are very similar to the
experimental results.
Predictions of Current Attachment at Thermionic Cathode for TIG Arcs
Authors: Tanaka Manabu , Yamamoto Kentaro , Shinichi Tashiro , Lowke John J.
Published: March 2009

Study of current attachment at thermionic cathode for TIG arc at atmospheric pressure is
attempted from numerical calculations of arc-electrodes unified model. The calculations show that
the maximum temperature of arc plasma close to the cathode tip for W-2% ThO2 reaches 19,000 K
and it is the highest value in comparison with the other temperatures for W-2% La2O3 and W-2%
CeO2, because the current attachment at the cathode tip is constricted by a centralized limitation of
liquid area of ThO2 due to its higher melting point. The calculations also show that, in cases of W-
2% La2O3 and W-2% CeO2, the liquid areas of La2O3 and Ce2O3 are widely expanded at the cathode
tip due to their lower melting points and then produce uniform current attachments at the cathode. It
is concluded that the current attachment at thermionic cathode is strongly dependent on work
function, melting point and Richardson constant of emitter materials.
Analysis of Weld Defects in Offshore Structural H Beams
Authors: Lee Hee Keun , Kim Jin Yong , Hwang In Hwan
Published: March 2009

H beam welds along rolling and transverse direction were investigated with
nondestructive testing, mechanical testing and microstructural analysis. Crack and fracture occurred,
during guided bend testing, in the specimens welded along rolling direction between flanges of the
H beams with higher S content although no defect was detected prior to the bend test. The fracture
seemed to be lamellar tearing because of step-like fracture propagation and terrace and wall fracture
appearance of the ruptured bend test specimen. On top of this, lamellar tear was already created in
the base metal area near the HAZ before the bend test in microstructural analysis on the welds. It
seems that lamellar tearing occurred in the specimens welded along rolling direction between
flanges of the H beams with higher S content as cracks were formed and propagated into a ferrite
phase region in α-γ band structure in combination with low ductility in transverse direction due to
MnS inclusions elongated along rolling direction.
Residual Stress Relief and Redistribution of Welded Metals by Vibratory Stress Relaxation
Authors: Kim B.J. , Son Y.R. , Yun J.O. , Lee Jeong Soo
Published: March 2009

In this study, research work on the effects of vibrational energy on the microstructure of
welds and Charpy toughness is performed. The results show that vibration during welding exhibits
positive effects on the microstructure constituent formation by reducing the amount and thickness
of grain boundary ferrite and suppressing the formation of the Widmanstatten structure. And also
due to the finer microstructure developed by the vibration, toughness value of the weld metal
increases.
Advanced Laser Joining by Use of Process Optimizing System Technology
Authors: Hoffmann Peter , Dierken Roland
Published: March 2009

Due to manifold variants of joining processes feasible by laser, new possibilities have
opened up in product design. An economic application of laser technology is usually connected to a
laser adapted modification of the part design and a laser system technology, which meets the
requirements of the chosen process in an optimum manner. For this contribution, three applications
have been chosen in order to demonstrate the versatility of the laser joining technology.
CW CO2 Laser Welding of Al-Mg Alloys with Filler Wires
Authors: Yoon Jong Won , Wallach E.R.
Published: March 2009

The CW CO2 laser weldability of various Al-Mg alloys was investigated in terms of weld
strength, ductility, Vickers hardness, formability and solidification cracking tendency when both
autogenous and wire feed welding were made. Tensile strength of the laser welds was lower than
that of the corresponding base metals, and it was linearly proportional to the Mg content of the weld
metal. Formability and ductility of Al-Mg alloy laser welds were lower than those of corresponding
base alloys as well. As for the weld solidification structure, as the Mg content increased in the weld
metal, more equiaxed grains developed. Hence, softening of weld metal and solidification cracking
were decreased in the weld metal containing higher Mg. Solidification cracking of Al-Mg alloy
laser welds showed the highest susceptibility at 1.6 to 1.9wt.% Mg, and it decreased with further
increase of Mg content.
Development of a Visual Monitoring System for Deformation Measuring of Welded Members and its Application
Authors: Han J.G. , Chang Kyong Ho , Jang Gab Chul , Hong K.K. , Cho Sam Deok , Kim Young Seok , Kim J.M. , Shin Y.E.
Published: March 2009

Recently, in the loading tests for steel members, the deformation value is measured by
calculating a distance of both cross-heads. This measuring method encounters a test error due to
various environmental factors, such as initial slip, etc.. Especially, in the case of welded members,
the non-uniform deformation behavior in welded joints is observed because of the effect of welding
residual stress and weld metal. This is mainly responsible for a test error and a loss of the reliability
for used test instruments. Therefore, to improve the accuracy and the applicability of measuring
system, it is necessary to employ a visual monitoring system which can accurately measure the local
and overall deformation of welded members.
In this paper, to accurately measure a deformation of welded members, a visual monitoring system
(VMS) was developed by using three-dimensional digital photogrammetry. The VMS was applied
to the loading tests of a welded member. The accuracy and the applicability of VMS was verified by
comparing to the deformation value measured by a test instrument (MTS-810). The characteristics
of the behavior near a welded joint were investigated by using VMS.
Characteristics of the Static and Dynamic Behavior of Steel Piles with a Welded Joint
Authors: Jang Gab Chul , Chang Kyong Ho
Published: March 2009

During welding process to make joints, residual stress is inevitably produced and weld
metal should be used. These influence the static and dynamic behavior of steel structures with welded
joints, such as steel piles. In steel structures, dynamic mechanical behavior is different to static
mechanical behavior. Therefore, to accurately predict the behavior of steel piles with a welded joint
under static-dynamic loading, the research on influence of a welded joint on the static and dynamic
behavior of steel piles is necessary. For that purpose, a rate-dependent plasticity model was used,
considering strain rate hardening and temperature rise.
In this paper, the distribution of welding residual stress in a welded joint was computed by using
three-dimensional heat conduction analysis and three-dimensional thermal elastic-plastic analysis.
The behavior of steel piles with a welded joint under axial static and dynamic loading was
investigated by using three-dimensional elastic-plastic finite element analysis, which employed a
rate-dependent plasticity model and included residual stress and mechanical properties of weld metal
in a welded joint. The rate-dependent plasticity model used in this paper is proposed by the authors
based on the static-dynamic loading tests. Numerical analysis results of steel piles with a welded joint
were compared to those without a welded joint. In comparison, the characteristics of static and
dynamic behavior of steel piles with a welded joint were investigated.
Experimental Investigations on Explosive Cladding of Cp-Titanium / AISI 304 Stainless Steel
Authors: Sartangi Pezhman Farhadi , Mousavi Seiyed Ali Asghar Akbari
Published: March 2009

The purpose of this study is to produce composite plates by explosive cladding process.
This is a process in which the controlled energy of explosives is used to create a metallic bond
between two similar or dissimilar materials. The welding conditions were tailored through parallel
geometry route by using different explosive ratios to produce both wavy and straight interfaces. In
this investigation, a two-pronged study was adopted to establish the conditions required for
producing successful solid state welding: (a) Analytical calculations to determine the weldability
window; (b) Metallurgical investigations of experiments carried out under different conditions. The
required parameters in the experiments were selected through numerical simulations. The analytical
calculations confirm the experimental results. Optical microscopy studies show that a transition
from a smooth to wavy interface occurs with increase in explosive ratio. Scanning electron
microscopy studies show the formation of intermetallic layer in the interface.
Reconfigurable 3D Laser-Stripe Sensor for Welding Processes
Authors: Kim Chang Hyun , Choi Tae Yong , Lee Ju Jang , Suh Jeong , Park Kyoung Taik , Kang Hee Shin
Published: March 2009

This paper describes the development of a reconfigurable 3D profile measurement
system for welding robot. The system consists of a PC based vision camera and a stripe-type laser
diode. The total system is assembled into a compact module which can be attached to the endeffector
of welding robots. Especially, the developed system is designed to operate at different
working distances. For this purpose, the reconfigurable mechanism which adjusts the focal length
and the relative position between the camera and the laser diode is devised. These two
configurations are automatically changing, according to the current working distance. Most parts of
image processing such as camera calibration, correction of distortion, and line extraction are
implemented and running on the PC. After measuring the welding profile, the 3D shape of the
parent metal is obtained and some useful features for robot manipulation are calculated.
Welding Technology of Lightweight Alloys
Authors: Kil Sang Cheol , Kim Hwan Tae
Published: March 2009

The trend of the welding technology of lightweight alloys such as aluminum alloy and magnesium
alloy has been studied. The lightweight alloys in the automobile, high-speed light aircraft and
modern aerospace industry can reduce vehicle weight, while stringently demanding the high quality
and efficienct welding techniques, to produce the best weldments. Among the production
technologies, welding plays an important role in the fabrication of lightweight vehicle structure.
This has led to an increasing attention towards the use of modern welding technology such as laser
beam welding process, ultrasonic welding process, friction stir welding technology and laser hybrid
welding technology, etc. This paper covers the recent technical trends of welding technologies of
lightweight alloys including the COMPENDEX DB analysis of welding metallurgy, welding
process, and welding fabrications.
Influence of HPT Deformation Temperature on Microstructures and Thermal Stability of Ultrafine-Grained Tungsten
Authors: Zhang Yue , Ganeev Artur V. , Gao X. , Sharafutdinov Alfred V. , Wang Jing Tao , Alexandrov Igor V.
Published: March 2009

In the present work high pressure torsion (HPT) was imposed on commercial purity (CP)
tungsten at different temperatures of 450 °С and 490 °С to achieve different microstructures and grain
boundary misorientation spectra (GBMS). After HPT at 450°С, ultrafine grained microstructure with
an average grain size of ~150 nm was developed in the metal. HPT at 490 °С results in an elongated
structures with average width of ~500nm. EBSD investigations showed that over 92% are HAGB
type in microstructure HPT-processed at 450°С, and in contrast, over 50% of grain boundaries are
LAGB in sample processed at 490°С. Annealing at 900°С for 1h, of the sample with homogeneous
UFG structure resulted from HPT at 450°C, leads to only limited decrease (~20%) in microhardness.
Chemical Sensitive Positron-Annihilation Study of Amorphization and Nanocrystallization Processes by Repeated Roll Bonding
Authors: Lechner Wolfgang , Puff Werner , Wilde Gerhard , Würschum R.
Published: March 2009

A positron annihilation study of free volumes was performed on Cu-Zr and Al-Sm alloys
in the course of repeated cold rolling (RCR) in order to contribute to the microscopic understanding
of the complex processes of solid-state amorphization and nanocrystallization. In addition to
positron lifetime spectroscopy, which yields information on the size of free volumes, twodimensional
Doppler broadening technique was applied in order to study the local chemical
environment of free volumes on an atomistic scale. Both in Cu60Zr40 and Al92Sm8 a characteristic
variation of the chemical environment of free volumes with the number of folding and rolling
(F&R) cycles could be observed. In the first (Al-Sm) and intermediate state (Cu-Zr) of F&R, free
volumes with an enhanced amount of Sm or Zr content in the local environment occur, indicating
interfacial segregation or the formation of solute-vacancy complexes. Upon further F&R cycling, a
complete (Cu-Zr) or partially amorphous structure (Al-Sm) is obtained with the free volumes
exhibiting a chemical environment characteristic of the average chemical composition. In contrast to
melt-spun or ball-milled amorphous alloys, free volumes of the size of a few missing atoms are
found in amorphous alloys prepared by RCR presumably due to strong athermal conditions of F&R
cycling.
Bond Strength of Ultrafine Grained Zr Fabricated by Accumulative Roll Bonding
Authors: Jiang Ling , Pérez-Prado Maria Teresa , Ruano Oscar , Kassner Michael E.
Published: March 2009

The bond strength of ultrafine grained Zr with a grain size of 0.4 µm, fabricated by
accumulative roll bonding (ARB), was assessed. The shear strength of the bond was estimated to be
about 20% of the shear fracture strength of the as processed metal, a ratio significantly higher than
that found in other materials processed by similar methods. The favorable degree of bonding
achieved is attributed to the high ductility of Zr as well as to the high reductions used during the
ARB process.
Compressive Behavior of Ultrafine-Grained Mg-Zn-Y-Zr Alloy Containing Quasicrystalline Phase
Authors: Zheng Ming Yi , Xu S.W. , Gan Wei Min , Wu Kun , Kamado Shigeharu , Kojima Yo , Brokmeier Heinz Günter
Published: March 2009

An ultrafine-grained (UFG) Mg-5.0wt%Zn-0.9wt%Y-0.2wt%Zr magnesium alloy with a
grain size of about 0.8 µm was produced by subjecting the extruded alloy to equal channel angular
pressing (ECAP) for 8 passes at 473 K. Compressive testing was performed on the ECAPed alloy in
a temperature range from 423 K to 523 K and under strain rates from 1.67×10-3 to 1.67×10-1 s-1. The
ultrafine grains of the ECAPed alloy were stable during compression because of the presence of the
dispersion of a fine quasicrystal I-phase and of precipitates in the alloy, which restricted grain
growth. The activation energy for the compression at the temperature range from 423 K to 523 K is
close to the value for grain boundary diffusion in magnesium, indicating that the compressive
deformation is mainly controlled by grain-boundary sliding.
Features of Work Hardening of Polycrystals with Nanograins
Authors: Kozlov Eduard , Koneva Nina , Trishkina L.I. , Zhdanov A.N. , Fedorischeva M.V.
Published: March 2009

The present work is devoted to the investigation of the influence of the grain size on the
main mechanical characteristics of nanopolycrystals of different metals. The Hall-Petch parameter
behaviour for Al, Cu, Ni, Ti and Fe was examined in the wide grain size interval. The stages of
plastic deformation and the parameters of work hardening for nanocrystalline copper were analysed
in detail. The deformation mechanisms and critical grain sizes accounting for the transition from the
dislocation slip to the grain boundary sliding were described.
Lattice Defects in Hydrogenated and HPT Processed Pd
Authors: Setman Daria , Krystian Maciej , Zehetbauer Michael J.
Published: March 2009

Pure palladium (99.95%) was hydrogenated, subsequently deformed by High Pressure
Torsion (HPT) and analyzed by differential scanning calorimetry (DSC). For comparison some
hydrogen-free HPT processed samples were also investigated. In case of the hydrogenated HPT Pd,
the concentration of single / double vacancies is noticeably higher. The importance of hydrogen for
the formation and stabilization of vacancy type defects and dislocations is discussed.
TEM Study of Local Disordering: A Structural Phase Change Induced by High-Pressure Torsion
Authors: Rentenberger Christian , Mangler Clemens , Scheriau Stephan , Pippan Reinhard , Karnthaler Hans Peter
Published: March 2009

Long-range ordered intermetallic alloys with L12 (Ni3Al, Cu3Au) and B2 (FeAl)
structures were deformed by high-pressure torsion at room temperature up to high grades of
deformation. Transmission electron microscopy shows that disordering caused by the deformation
occurs on a very local scale within coarse grains along glide planes (Cu3Au, Ni3Al) and in the form
of well defined local regions (Ni3Al, FeAl). The latter leads to a duplex structure consisting of an
ordered coarse-grained structure and a disordered nanocrystalline structure. The different
mechanisms that can lead to disordering during severe plastic deformation are discussed on the
basis of the different ordering energies and on the basis of antiphase boundaries associated with
gliding dislocations. The results indicate that in intermetallic alloys the formation of a
nanocrystalline structure by severe plastic deformation is facilitated by the loss of order.
Grain Boundary Structure and Deformation Defects in Nanostructured Al–Mg Alloys Processed by High Pressure Torsion
Authors: Liu M. , Roven Hans Jørgen , Ungár Tamás , Balogh L. , Murashkin Maxim Yu. , Valiev Ruslan
Published: March 2009

An Al–0.5 Mg alloy and a commercial AA5182 alloy were subjected to high pressure torsion
(HPT) to five turns under pressure of 6 GPa at room temperature. The grain boundary structure and
deformation defects were investigated after HPT using high-resolution transmission electron microscopy
(HRTEM). Low-angle, high-angle, equilibrium and non-equilibrium grain/subgrain boundaries, twin
boundaries, full dislocations, dipoles, microtwins and stacking faults were identified by HRTEM. Extrinsic 60°
dislocations in the form of dipoles were frequently observed in non-equilibrium grain/subgrain boundaries. In
addition subgrain size distributions and dislocation densities were quantified by x-ray line profile analysis. It
was observed that the average grain size decreased from about 120 nm to 55 nm as the Mg content increased
from 0.5 to 4.1 wt%. Concomitantly the average stored dislocation density increased from 1.7 to 12.8  1014
m-2. Based on the HRTEM investigations and the x-ray line profile analyses, the deformation mechanism
associated with the typical grain boundaries and deformation defects in the aluminium alloys were discussed.
Microstructure and Mechanical Properties of Commercial Purity HIPed and Crushed Aluminum
Authors: Bui Quang Hien , Dirras Guy F. , Hocini A. , Ramtani Salah , Abdul-Latif Akrum , Gubicza Jenő , Chauveau Thierry , Fogarassy Z.
Published: March 2009

Ultrafine-grained aluminum microstructures were processed from commercial purity
powder by combining hot isostatic pressing (HIP) and dynamic severe plastic deformation (DSPD).
After the first step, the bulk consolidated material showed a random texture and homogeneous
microstructure of equiaxed grains with an average size of 2µm. The material was then subsequently
impacted, using a falling weight at a strain rate of 300s-1. The resulting material showed a
microstructure having an average grain size of about 500 nm with a strong gradient of fiber-like
crystallographic texture parallel to the impact direction. The mechanical properties of the impacted
material were subsequently characterized under compressive tests at room temperature at a strain
rate of 10-4s-1. The effect of the change of the deformation path on the mechanical response parallel
(DN) and perpendicular (DT) to the impact direction was also investigated. These results are here
discussed in relation with microstructure and texture evolution.
Tensile Property of Submicrocrystalline Pure Fe Produced by HPT-Straining
Authors: Todaka Yoshikazu , Miki Yoshii , Umemoto Minoru , Wang Chao Hui , Tsuchiya Koichi
Published: March 2009

The microstructure and the mechanical properties of pure Fe after HPT-straining at a
rotation-speed of 0.2 rpm under a compression pressure of 5 GPa were investigated. The elongated
grains with 300 nm thick and 600 nm long were observed at r = 1.5 mm away from the disk center
regions after HPT-straining for 5 turns ( εeq = 45). The obtained Vickers microhardness in the
submicrocrystalline Fe after 5 turns was around Hv 3.6 GPa. The engineering tensile strength and
total elongation of the HPT-processed Fe for 10 turns were 1.9 GPa and 30 %. These facts suggest
that HPT-straining leads to significant refinement of microstructure and increase in strength with
good ductility.
Microstructure Evolution during Continuous Frictional Angular Extrusion of Interstitial-Free Steel
Authors: Yan Bo , Dover Shane , Jin Lan , Shen J. , Huang Yan , Jiao S.
Published: March 2009

Interstitial-free steel sheets have been processed using a novel severe plastic deformation
technique - continuous frictional angular extrusion (CFAE), in order to produce ultrafine grained
structures. The deformation was carried out at room temperature and individual sheet specimens were
repeatedly processed to various passes. An overall grain size of 200nm was achieved after 8 passes (or
an equivalent total strain of 5.3). The present paper reports the evolution of microstructures during
deformation, which were examined and characterized using electron backscatter imaging and high
resolution EBSD in a field emission gun SEM. The mechanisms of grain refinement are discussed.
Precipitation Studies of Undeformed and ECAP-Deformed Al-4%Cu Alloys: Effects on Microstructure and Tensile Properties
Authors: Prados Erika Fernanda , Sordi Vitor Luiz , Ferrante Maurizio
Published: March 2009

The present study is an assessment of the effects of precipitation heat treatments on
tensile behaviour, work hardening (WH) characteristics and microstructural evolution of an
Al-4%Cu alloy deformed by equal channel angular pressing (ECAP). Two ageing temperatures
were employed (170 and 100oC) and their effect on strength and WH behaviour was compared with
that exerted on the same alloy, but in two different initial conditions: quenched from solution
temperature and slowly cooled before anneal. Grain and precipitate sizes of samples deformed by
one and four ECAP passes and heat treated as described were measured employing transmission
electron microscopy (TEM). It was concluded that the lower ageing temperature gives the best
combination of strength and ductility, a high WH rate and, possibly, the smaller grain and
precipitate sizes. The relative participation of the various hardening mechanisms to total strength
was estimated from tensile tests and hardness measurements.
Grain Boundary Structures of ARB Processed Aluminum
Authors: Ii Seiichiro , Hishida Motoki , Takata Naoki , Ikeda Kenichi , Nakashima Hideharu , Tsuji Nobuhiro
Published: March 2009

Grain boundary structures in the commercial purity aluminum (1100Al) highly deformed
by the accumulative roll bonding (ARB) process was observed by using conventional transmission
electron microscopy (CTEM) and high resolution transmission electron microscopy (HRTEM). In
the low angle grain boundary with a tilt angle (2θ) of 2.1o consisted of the periodic dislocations
array, the interval of those dislocations could be explained by the dislocation model for grain
boundary. However, the dense dislocation region locally existed at the vicinity of the low angle
boundary. On the other hand, we also observed the high angle grain boundary of which the common
axis and 2θ was <110> and 125.9o, respectively. In this grain boundary, we could describe the
boundary configuration in terms of the combination of the kite-shaped structure unit characterized
by Σ11 coincidence boundary with the 2θ of 129.52o around <110> and the additional dislocations
to compensate the difference of the actual and geometrically coincided one.
Production of Nanostructure in Titanium by Cold Rolling
Authors: Malysheva Svetlana , Salishchev G.A. , Mironov Sergey , Zherebtsov Sergey V.
Published: March 2009

The paper considers changes in microstructure, texture and mechanical properties of
commercial titanium with initial coarse-grained structure during cold sheet rolling. It has been
shown that rolling above 75% leads to formation of a uniform nanocrystalline (NC) structure with a
grain size of approximately 0.2 'm in the sheet material. The sheets have a high level of mechanical
properties which is comparable with the properties of bulk specimens of titanium with NC structure
produced by some other method of severe plastic deformation.
Cycling of Ultrafine-Grained Ti-6Al-4V ELI Alloy: Microstructural Changes and Enhanced Fatigue Limit
Authors: Saitova Lilia R. , Höppel Heinz Werner , Göken Matthias , Kilmametov A.R. , Semenova Irina P. , Valiev Ruslan
Published: March 2009

Ti-6Al-4V ELI (extra low interstitials) was processed by equal channel angular pressing
in order to obtain an ultrafine-grained (UFG) microstructure which is known to enhance the fatigue
behavior of metallic materials. Fatigue properties of UFG Ti-6Al-4V ELI were studied by strain
and stress controlled fatigue tests. UFG Ti-6Al-4V ELI shows an improvement of the fatigue
behavior compared to conventional grain (CG) size counterpart. Microstructural investigations prior
to and after fatigue testing confirm a high structural stability of the UFG material. Hence, the UFG
alloy has a high potential for prospective use in biomedical and engineering applications.
Deformation Behaviour of Accumulative Roll Bonded and Friction Stir Welded Aluminium Alloys
Authors: Topic Irena , Höppel Heinz Werner , Göken Matthias
Published: March 2009

Commercial purity aluminium AA1050 and aluminium alloy AA6016 were accumulative
roll bonded and subsequently friction stir welded. The microstructure of the conventional and
ultrafine-grained materials produced by accumulative roll bonding is strongly affected by friction
stir welding. The elongated ultrafine-grained microstructure of roll bonded sheets becomes coarser
and equiaxed in the nugget region. Hydraulic bulge tests showed that higher burst pressure can be
achieved for samples without friction stir welding than for the ones with friction stir welding.
Localised deformation, crack initiation and propagation, as well as the final fracture occurred within
the nugget. Friction stir welded AA1050 sheet showed similar achievable burst pressures and von
Mises equivalent strains compared to the as-received conventionally grained sheets. On the other
hand, significantly higher burst pressures and at the same time higher von Mises equivalent strains
were observed for the friction stir welded ultrafine-grained material than for the friction stir welded
conventionally grained material.
Cyclic Deformation Behaviour and Fatigue Lives of Ultrafine-Grained Aluminium-Magnesium Alloys
Authors: Höppel Heinz Werner , May Johannes , Göken Matthias
Published: March 2009

The fatigue behaviour of aluminium-magnesium alloys has been investigated in the
recrystallized CG state and in an ultrafine-grained (UFG) state after equal channel angular pressing
(ECAP). A strong improvement of the fatigue behaviour up to 12 ECAP passes has been found for
an AlMg0.5 alloy. The results have been interpreted in consideration of the microstructure of the
different states. Additionally, for an investigation of the influence of impurities on the cyclic
stability of Aluminium, 3 different AlMg alloys with Magnesium contents of 0.5, 1, and 2 wt.-%
have been compared. Total strain controlled fatigue tests have shown an improvement of the cyclic
stability with increasing Mg content.
Microstructural Evolution and Creep of an Al-0.2wt.%Sc Alloy after Equal-Channel Angular Pressing
Authors: Král Petr , Dvořák Jiří , Sklenička Václav
Published: March 2009

Experiments were conducted on an Al-0.2wt.%Sc alloy to evaluate the effect of equalchannel
angular pressing (ECAP) on its creep behaviour. ECAP was conducted at room temperature
with a die that had an internal angle of 90° between the two parts of the channel. The subsequent
extrusion passes were performed by route BC up to 8 ECAP passes. Creep tests in tension were
performed on the as-pressed samples at 473 K under an applied stress range between 10 to 50 MPa.
For comparison purposes, some creep tests were performed also on the unpressed alloy. Following
ECAP and creep testing, samples were prepared for examination by means of transmission electron
microscopy (TEM) and scanning electron microscopy (SEM) equipped with an electron back
scattering diffraction (EBSD) unit. The observation of the surface of the ECAPed samples after
creep exposure showed the occurrence of mesoscopic shear bands. The EBSD data reveal that these
bands are separated by high angle grain boundaries. The creep resistance of an alloy is a little
decreased after one ECAP pass. However, successive ECAP pressing lead to a noticeable decrease
of the creep properties. Thus, the Al-0.2wt.%Sc alloy processed by 8 ECAP passes exhibited faster
creep rate by about two and/or three orders of magnitude than the unpressed alloy when creep
testing at 473 K and at the same applied stress. The detrimental effect of ECAP on the creep
resistance is probably a consequence of a synergetic effect of mesoscopic sliding of groups of
grains along shear bands, more intensive grain boundary sliding and creep cavitation in creep of the
ultrafine-grained material.
Microstructural Stability and Creep in Nanocrystals
Authors: Chokshi Atul H.
Published: March 2009

Microstructural stability is an important consideration during high temperature deformation and
processing of nanomaterials. We will address issues relating to triple junctions in limiting grain
growth during creep as well as densification. Although early studies on deformation have
considered diffusion creep as a possible rate controlling deformation mechanism in nanocrystals, a
critical inspection of available data indicates that there is no strong evidence for conventional
diffusion creep in such materials. The possibility of diffusion creep by rapid diffusion along triple
junctions will be analyzed, and interface controlled diffusion creep will also be discussed critically.
It is shown that the critical grain size for dislocation activity is similar to that for occurrence of
conventional diffusion creep.