221 BNM-2007, Special Oral Session for Young Scientists (PhDs and PhD Students), 17 August 2007 Oral report Grain Boundary Precipitation Behavior of Nanostructured Maraging Steel Syamak Hossein Nedjad a,1 and Mahmoud Nili Ahmadabadi b,2 a Faculty of Materials Engineering, Sahand University of Technology, P. O. Box: 51335-1996, Tabriz, Iran. b School of Metallurgy and Materials Engineering, University of Tehran, P. O. Box: 14395-731, Tehran, Iran. 1 [email protected] , 2 [email protected]An Fe-Ni-Mn maraging alloy was cold rolled for 85% at room temperature and isothermally aged at 753 K. Transmission electron microscopy was used to study precipitation behavior at grain boundaries during isothermal aging. It was indicated that severe cold rolling and aging treatment transforms initial lath martensite microstructure to a partially nanostructured steel. In the areas containing equiaxed nano-scale grains, coarsening of grain boundary precipitates was found to proceed in a rather homogeneous dissolution of fine precipitates at grain interiors. The augmented homogeneous dissolution of precipitates at nano-scaled grain interiors is attributed to high density structural defects facilitating lattice diffusion of alloying elements. Arrays of precipitates were found at elongated grain boundaries in the initial stages of aging. However, matrix precipitates at elongated grains were identified larger than precipitates at equiaxed nano-scale grains. 200 300 400 500 600 700 1 10 100 1000 Time, ks Hardness, HV 0 Figure 1. Changes in hardness of the cold rolled steel during isothermal aging at 753 K
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221
BNM-2007, Special Oral Session for Young Scientists (PhDs and PhD Students), 17 August 2007 Oral report
Grain Boundary Precipitation Behavior of Nanostructured Maraging Steel Syamak Hossein Nedjada,1 and Mahmoud Nili Ahmadabadib,2
a Faculty of Materials Engineering, Sahand University of Technology,
P. O. Box: 51335-1996, Tabriz, Iran. b School of Metallurgy and Materials Engineering, University of Tehran,
An Fe-Ni-Mn maraging alloy was cold rolled for 85% at room temperature and isothermally
aged at 753 K. Transmission electron microscopy was used to study precipitation behavior at
grain boundaries during isothermal aging. It was indicated that severe cold rolling and aging
treatment transforms initial lath martensite microstructure to a partially nanostructured steel.
In the areas containing equiaxed nano-scale grains, coarsening of grain boundary precipitates
was found to proceed in a rather homogeneous dissolution of fine precipitates at grain
interiors. The augmented homogeneous dissolution of precipitates at nano-scaled grain
interiors is attributed to high density structural defects facilitating lattice diffusion of alloying
elements. Arrays of precipitates were found at elongated grain boundaries in the initial stages
of aging. However, matrix precipitates at elongated grains were identified larger than
precipitates at equiaxed nano-scale grains.
200
300
400
500
600
700
0.1 1 10 100 1000Time, ks
Har
dnes
s, H
V
0
Figure 1. Changes in hardness of the cold rolled steel during isothermal aging at 753 K
222
a b
c d
Figure 2. Transmission electron micrographs of a specimen aged for 0.36 ks; (a) and (b) show grain boundary precipitates (arrows) at nano-scale grain boundaries; (c) and (d) show arrays of aligned precipitates (arrow) at
elongated grain boundaries
a b
Figure 3. Transmission electron micrographs of a specimen aged for 86.4 ks; (a) bright field image showing coarse precipitates at grain “A”; (b) dark field image lightening precipitates. Matrix precipitates in the nano-
scale grains (A) are smaller than precipitates at elongated grain “B”
223
BNM-2007, Special Oral Session for Young Scientists (PhDs and PhD Students), 17 August 2007 Oral report
Microstructural Stability of UFG IF Steel Under Cyclic and Thermal Loading Thomas Niendorfa,1, Hans Jürgen Maiera,2 and Ibrahim Karamanb,3
a Lehrstuhl für Werkstoffkunde (Materials Science), University of Paderborn,
33095 Paderborn, Germany b Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843, USA
In the present work we investigated the cyclic stress-strain behavior of body-centered cubic
(bcc) ultrafine-grained (UFG) interstitial free (IF) steel under cyclic and thermal loading. The
fatigue behavior of UFG bcc materials has been only investigated in a small number of
studies, while no study systematically reported on the behavior under additional thermal
loading, yet.
In previous studies of our group it has been shown that the damage mechanisms that lead to
the low fatigue lives of UFG Copper, dynamic recrystallization / grain growth do not appear
in the UFG IF steel, when the fatigue experiments are conducted at room temperature. The
microstructural stability led to an increased fatigue performance in comparison to the coarse
grained material [1].
In the present study the fatigue behavior of UFG IF steel from route 8E at temperatures
ranging from room temperature up to 440 °C is investigated. All tests were conducted under
strain control with constant strain amplitude of 0.28% and a strain rate of
6 x 10-3 s-1.
The results of the current work can be summarized as follows:
The fatigue life of the UFG IF steel decreases with increasing test temperature. This behavior
is caused by strain localization due to local grain coarsening. These findings are supported by
results from electronoptical measurements, such as electron backscattering diffraction
(EBSD).
The UFG IF steel shows even at the high test temperatures cyclic hardening. This behavior
seems to be caused by a mechanism that is similar to strain aging.
[1] T. Niendorf, D. Canadinc, H.J. Maier, I. Karaman, S.G. Sutter, Int. J. Mater. Res., 97
(2006) 1328
224
BNM-2007, Special Oral Session for Young Scientists (PhDs and PhD Students), 17 August 2007 Oral report
Accumulative Roll-Bonding (ARB), Mechanical Properties and Deformation Behaviour of Aluminium AA1050 and Aluminium Alloy AA6016
Irena Topica,1, Heinz Werner Höppela,2 and Mathias Gökena,3 a Friedrich-Alexander University Erlangen-Nürnberg, Institute of General Materials Properties,
Very little information is available on the stability of ultrafine grained age-hardening
aluminium alloys at elevated temperatures and the resulting mechanical properties [1,2].
Therefore the objective of the present work is the investigation of the mechanical properties
and microstructure of the commercial aluminum alloys AlMg0.5Si0.4 and AlSi1Mg0.7Mn0.6
(AA6063 and AA6082) with ultrafine grain size after annealing. The materials were
processed by equal channel angular extrusion (ECAE) at room temperature up to total strains
of ~9.2 in the solution heat treated plus water quenched (W) and the peak aged condition
(T6). Hardness measurements were used initially to characterize the behaviour during
isothermal annealing at temperatures between 100°C and 400°C. Subsequently characteristic
states were selected for tensile and Charpy impact toughness testing. Generally, the aging and
recovery/recrystallisation kinetics are similar for both alloys, to the same alloying system. For
the AA6082 significantly smaller grain sizes and about 30 % higher strengths are achieved
compared to the AA6063 with lower alloying content in the as-processed condition. The
deformation of the AA6082 requires 100 MPa backpressure to assure homogeneous plastic
flow while the AA6063 can be processed without additional precautions. The post-ECAE
strengths of the peak aged alloys are slightly higher compared to the materials processed in
the solution heat treated condition. Depending on the annealing temperature the strength
decreased continuously in two stages (recovery and recrystallisation) for the material
processed in the T6 condition. Different behaviour was found for the material processed in the
W condition. An increase in both post-ECAE strength and ductility was found up to a total
strain of ~2.3 during annealing, both the ultimate tensile strength and uniform elongation can
be enhanced for ~40 % compared to the coarse grained commercial material when the
material is ECAE-processed before ageing (see Fig. 1).
231
At strains above ~4.6 this effect of additional
precipitation hardening during annealing is
overcompensated by the significant decrease of
micro-strains, as reported in the literature [3].
The ductility also decreases. The changes of
mechanical properties were found to be more
pronounced at lower annealing temperatures.
These findings are supported by comprehensive
micro-structural investigations. The study shows
that ECAE has the potential to significantly
improve the production efficiency and
mechanical properties of semifinished parts
made of commercial age-hardening Al alloys. The authors gratefully acknowledge the
Deutsche Forschungsgemeinschaft (DFG) for supporting this work carried out within the
framework of project SFB 692.
[1] J. Wang, Y. Iwahashi, Z. Horita, M. Furukawa, M. Nemoto, R.Z. Valiev, T.G. Langdon,
Acta Mater., 7 44 (1996) 2973
[2] N. Gao, M. Starink, M. Furukawa, Z. Horita, Ch. Xu, T.G. Langdon, Mat. Sci. Forum,
503-504 (2006) 275
[3] E. Cerri, P. Leo, Mat. Sci. and Eng. A, 410-411 (2005) 226
Figure 1. Engineering stress–strain curves from tensile tests for the UFG-AlMg0.5Si0.4 without and with annealing
232
Figure 1. Foils and Bars of Nanostructured Cu (top) and Inconel 718 (bottom)
BNM-2007, Special Oral Session for Young Scientists (PhDs and PhD Students), 17 August 2007 Oral report
Bulk Nanostructured Materials by Large-Strain Extrusion Machining and Micro/Meso Scale Components Thereof
Christopher Saldanaa,1, Wilfredo Moscosoa,2, James B. Manna, M. Ravi Shankara,
Srinivasan Chandrasekara, W. Dale Comptona, Alex H. Kinga, Kevin P. Trumblea and
Pin Yangb a School of Industrial Engineering, Purdue University, West Lafayette, IN, USA b School of Materials Engineering, Purdue University, West Lafayette, IN, USA
b Sandia National Laboratories, Albuquerque, NM, USA
BNM-2007, Special Oral Session for Young Scientists (PhDs and PhD Students), 17 August 2007 Oral report
Consolidation of Nanocrystalline AlMg4.8 Powder via ECAP Back Pressure Marco Hüllera,1, Johannes Vlceka,2 , Heinz Werner Höppelb,3 and Mathias Gökenb,4
a EADS Deutschland GmbH, EADS Innovation Works, 81663 München, Germany b Department of Materials Science and Engineering, Institute I: General Materials Properties WWI,
and V.P. Soloviev, Mater. Sci. Forum, 503-504 (2005) 693
244
BNM-2007, 17 August, Poster Session C Poster report
Computer Simulation of Material Flow during Equal-Channel Angular Pressing Vladimir Zhernakova, Igor Budilova, Igor Alexandrovb,1
a Ufa State Aviation Technical University, 12 K. Marx St., Ufa 450000 Russia b Institute of Physics of Advanced Materials, Ufa State Aviation Technical University,
Material flow has a complicated character in the conditions of severe plastic deformation
(SPD) realized by equal-channel angular (ECA) pressing. The latter is defined by the type of
crystalline lattice, character of strain hardening in material, its contained plasticity,
temperature and strain rate, geometry of the channels in the die-set, friction coefficient
between die-set walls and the surface of the deformed billet etc. On the other hand,
controlling the character of material flow, volume and shape of the deformation zone can
provide an optimum level and distribution of accumulated strains in the body of a deformed
billet. Computer simulation by means of finite element method is one of the most effective
tools for conducting such a research.
The report presents the results of 3D modeling of the processes of material flow during ECA
pressing of Ti billets. Influence of the character of strain hardening, number of passes, route
on the value of accumulated strains and their intensity was studied. Conclusion about
potential areas of crack nucleation during realization of different passes of a billet through the
die-set channels was made.
245
BNM-2007, 17 August, Poster Session C Poster report
The Effects of Conventional direct Extrusion of the Twist Extruded Ti-6Al-4V by Means of Finite Element Method
Amir R. Shahab1, S.A.A. Akbari Mousavi2, M. Mastoori3 School of Metallurgy and Materials Engineering, School College of Engineering, University of Tehran,
Figure 1. TEM observation of BF distortion near possible disclination location. (a)-(d) consecutive images of the BF run in deformed alloy Cu-Zn (23%). Image size is 1.5x1.5 µm
Figure 2. Modeled TEM image of BF near a disclination dipole. Disclination strength ω=1o; foil thickness 200nm, extinction length ≈gξ 40.9nm.
Coordinates are in units of gξ
262
BNM-2007, 17 August, Poster Session C Poster report
A Study on Hard Cyclic Viscoplastic Deformation Behavior of Bulk UFG Metals Lembit Kommel
Tallinn University of Technology, Department of Materials Engineering
The features of room temperature failure in 20mm plates of commercial aluminum alloys
1560 (Al-6.5Mg-0.6Mn) and 5083 (Al-4.4Mg-0.7Mn-0.15Cr) with fragmented and grained
submicrocrystalline (SMC) (d~0.4-0.5µm) and microcrystalline (MC) (d~5-8µm) structures
processed by severe plastic deformation (SPD) via complex angular extrusion and following
annealing are considered.
The analysis of pre-polished surfaces of tensile specimens has shown that irrespective the
alloys microstructure the fracture starts by microcracks opening in coarse primary particles of
excess phases and their penetration into the aluminum matrix. At strain increase the new
cracks are formed predominantly by particles brittle failure and the occurrence of these
processes is more intense in the SMC alloys (Fig.
1).
It has been revealed that less resistance to cracks
formation in submicrocrystalline structures is
attributed to earlier and stronger localization of
plastic deformation in aluminum matrix which is
accompanied by formation of coarse shear bands
passing through hundreds of grains. Concurrently
with the development of such a band structure
homogeneous initiation of cracks at grain
boundaries and in triple junctions occurs. As for
the MC alloys, the conditions for stress cracks
formation are realized at later stages of plastic deformation (at higher strains) in short
individual slip lines compatible with their grain size.
The data on qualitative analysis of the path of macrocrack growth and quantitative estimation
of energy expenditures spent on formation of free fracture surfaces (via surface area) and
plastic deformation at the crack tip (via size of plastic deformation zone (PDZ)) under
Figure 1. Microcrack density vs tensile strain of the 1560 alloy
Степень деформации, %0 2 4 6 8 10 12 14 16
Плотность
микротрещ
ин, м
м-2
0
200
400
600
800
1000
аб
Плотность трещин в сплаведо растяжения
SMCМC
Strain, %
Mic
rocr
ack
dens
ity, m
m-2
After SPD
269
bending tests are shown and discussed. In particular, it has been established that
transformation of the fragmented SMC structure into the MC grained one due to post-SPD
annealing leads to the change in the character of failure from brittle intercrystalline to ductile
transcrystalline one. This is accompanied by the deviation of the crack from the normal to the
axis of applied tensile stresses and the increase in crack surface area.
It has been concluded that the main factor determining the resistance to crack growth in SMC
and MC alloys is the size of PDZ at the crack tip. The dependences of PDZ size and crack
resistance parameters on structure of the alloys matrix are similar: the PDZ size and the
specific works of the alloys failure and crack growth are smallest in the SMC fragmented
materials, while in the MC alloys they
are largest (Fig. 2).
Besides, the fracture character essentially
depends on the observed distinction in
the changes of the alloys phase
composition upon annealing. Thus,
unlike 1560, the formation of SMC grain
structure in 5083 alloy upon low
temperature post-SPD annealing was
accompanied by the dissolution of
second β-phase (Al3Mg2) precipitates
formed at deformation processing and
the proportional increase in the PDZ size
and SMC alloy resistance to crack
growth which values become close to the ones apt to the alloy with MC structure.
Figure 2. Specific work for specimen failure and crack growth vs the size of plastic deformation zone at the crack tip in the 1560 alloy
050
100150200250300350400
2 3 4 5 6 7
PDZ size, mm
Spec
ific
wor
k, k
J/m
2
Роста трещины
РазрушенияММCC
SSMMCC
Crack growth Fracture
270
BNM-2007, 17 August, Poster Session C Poster report
Pressure Welding of VT6 Titanium Alloy under Conditions of Low Temperature Superplasticity
Minnaul Kh. Mukhametrakhimov, Ramil Y. Lutfullin and Amir K. Galimov Institute for Metals Superplasticity Problems, RAS, 39 Khalturin St., Ufa 450000, Russia
The essential role of deformation processes occurring at pressure welding under conditions of
“low temperature superplasticity” arises urgent necessity in thorough analysis of the strain-
stress state in the zone of joining.
Conditions of low temperature
pressure welding have been modeled
using FE-code ANSYS 5.7.
The goal of investigations was to
optimize the neck geometry and
parameters of the strain-stress state of
contacting processed sheets for
analyzing processing and reducing
sound composition to components of
one-axial interaction. Such an
approach allows performing controlled
deformation in the zone of welded
joint and provides optimal
(appropriate) temperature-strain rate
conditions of deformation under
relatively low pressure.
Unlike the sample with the constant cross section area the sample with the alternating area is
distinguished by the at once occurrence of local deformation since the laws of its development
are different in these samples. Thus, varying the sample shape one can control the time of
neck occurrence and change the laws of its development. At that the basic deformation is
localized in the zone of joint providing the best weldability of the construction. Imparting a
cylindrical shape to the welded sample with a less cross section area promotes steady
localization of plastic flow.
Figure 1. Normal stress in the sample with the constant cross section area and marked near-contact zone
271
a b Figure 2. Micrographs of the solid state joint for the VT6 alloy after pressure welding at 600 (а) and 650оС (b)
under condition s of low temperature superplasticity
Using the results of modeling a full-scale experiment was carried out. The experiment on
pressure welding of bulk samples of nanocrystalline titanium alloy VT6 at 600oC was aimed
to produce a joint having a tensile strength above 1150 MPa at room temperature.
One of the most important processing aspects is application of nano- and submicrocrystalline
alloys as sheet inserts for solid state joining of large-scale bulk semi-products. The decreased
flow stress of the NC material of the insert under similar temperature conditions provides
localization of superplastic deformation in the zone of joining. Moreover, the processed
mechanical properties of the zone of joining are similar to the ones of the welded semi-
products.
0
200
400
600
800
1000
1200
0 2 4 6 8 10 12 14 16 18 20
Степень деформации, %
Напряжения
течения
, МПа
- а) - б)
а b c
Figure 3. Micrographs of solid state joint (а;b) and mechanical properties of VT6 alloy (c) after pressure welding at 650оС using sheet inserts of nanocrystalline (a) and submicrocrystalline VT6 alloy (b).
The application of nanocrystalline and submicrocrystalline sheet inserts provides sound solid
state joining at lower temperature (T) and welding pressure (P) as compared to traditional
superplasticity. The obtained result is of practical importance for machine building and open
premises for developing recourse saving processing methods applying nanocrystalline
materials.
272
BNM-2007, 17 August, Poster Session C Poster report
Processing and Mechanical Properties of Bulk Nanostructured Nickel-Based Alloys
Shamil Mukhtarova,1, Nadezhda Dudovaa,2 and Vener Valitova,3 a Institute of Metals Superplasticity Problems RAS, 39 Khalturin St., Ufa 450001, Russia
At present the mechanisms of grain boundary (GB) diffusion in nanostructured metals is one
of the least understood phenomena. Some experimental data indicate on a many orders of
magnitude enhancement of the GB diffusion coefficient in bulk nanomaterials as compared to
that in ordinary polycrystals, while others shown only an insignificant increase. Theoretical
analyses available in literature are mainly of a phenomenological character and do not provide
a sufficiently clear insight into the problem.
Atomistic computer simulation of grain boundaries and their junctions is an important tool for
elucidating the mechanisms and kinetics of diffusion in nanomaterials. In particular, an
information obtained on the energetics of point defects in GBs and their dependence on the
GB structure is very useful for an approximate comparison of the GB diffusion coefficients in
equilibrium and nonequilibrium GBs. Recently the authors have studied vacancy formation
and migration energies in special [001] tilt GBs in Ni containing extrinsic GB dislocations
and disclinations [1-3]. However, most of the GBs in real nanomaterials have a general
character and study of the properties of vacancies in such GBs seems very important.
The present paper is devoted to a computation and analysis of the vacancy formation energies
in a general twist GB in Ni containing a positive or negative wedge disclination with the
strengths equal to ω=-5.0° and ω=5.0°, respectively. The GB has a plane (310) and twist
misorientation angle 76.7°. The zero-temperature relaxation resulted in a fairly wide (7 Å) GB
region with an amorphous atomic structure. For this thickness, one period of the GB contains
269 atoms. By a successive removal of each of these atoms followed by relaxation, vacancy
formation energy on each site was calculated for this equilibrium GB. By a removal or
insertion of a wedge of material into one half of the GB positive and negative wedge
disclinations were created in the GB. The displacement fields of the disclinations were
calculated for a cylinder with radius R=100 nm in order to catch the influence of disclinations
on vacancy energies in bulk nanomaterials with the grain size of the same order. Then the
vacancy energies on all 269 sites were calculated for the GB periods lying on distances of 5.4,
9.0, and 12.6 nm from the disclination line.
274
The results show that the GB vacancy
energies have a bimodal distribution
(see, for example, the figure). In the
equilibrium GB the first peak is at 0.18
eV and the other at 1.33 eV (the lattice
vacancy energy is equal to 1.63 eV for
the embedded atom method used). The
stresses of a negative disclination result
in a 0.15 eV shift of the low-energy peak
to the left, while those of the positive disclination result in an opposite shift to the same value.
The vacancy formation energy averaged over all 269 positions is equal to 0.84 eV in the
equilibrium GB, 1.00 eV in the GB with negative disclination and 0.65 eV in the one with
positive disclination. Thus, the disclination stress fields can result in a significant, up to 0.2
eV change of the vacancy formation energies in general GBs.
[1] R. T. Murzaev and A. A. Nazarov, Phys.Metals Metallogr., 100 3 (2005) 228
[2] R. T. Murzaev and A. A. Nazarov, Phys.Metals Metallogr., 101 1 (2006) 86
[3] R. T. Murzaev and A. A. Nazarov, Phys.Metals Metallogr., 102 2 (2006) 198
Figure 1. The distribution of vacancy formation energies in an equilibrium (310) twist GB in Ni
275
BNM-2007, 17 August, Poster Session C Poster report
Diffusion-Controlled True Grain-Boundary Sliding in Nanostructered Metals and Alloys
Evgeny F. Dudareva,1, Galina P. Pochivalovaa, Yury R. Kolobov b,
Evgeny V. Naidenkinc and Oleg A. Kashinc a Siberian physical technical institute TSU, 1 Novosobornaya Sq., Tomsk 634050, Russia b Center for NanoStructured Materials and Nanotechnologies, Belgorod State University,
85 Pobeda St., Belgorod 308015, Russia c Institute of strength physics and materials science SB RAS,
Comparison of mechanical characteristics and failure peculiarities of Ti-6Al-4V ELI alloy at
300, 77 and 4.2 К under uniaxial compression and tension in the different structural sates [1]
was done. In the initial coarse grained state 1, average grain size (d) of α-phase is 10-25 µm.
Ultra-fine grained state 2 was produced from the state 1 through equal channel angular
pressing (ECAP) and has d value of ~ 0.5 – 1 µm. State 3 was obtained from the state 1 by the
thermal treatment, ECAP and an extrusion; average size d of α-graines is from 200 nm to
400 nm. Mechanical characteristics were investigated with a stiff testing machine, at strain
rate 5⋅10-4 s-1 , at 300, 77 and 4.2 K. Specimens for compression had a rectangular shape
(2×2×7 mm), and specimens for tension have dog-bone shape with the 5.5 mm gage length
and a square cross section of 0.75 × 2.4 mm2.
It is established that reducing of the grain size from the state 1 (d~ 10-25 µm) to the state 2 (d
~ 0.5 – 1 µm) leads to increasing of the yield stress σ0 and strength σf up to 50 % in the entire
temperature interval, moreover σ0 and σf values at the compression exceed corresponding
values under tension. Further decrease of the grains size (state 3) down to 200 nm - 400 nm
results in the additional increment of σ0 and σf for 25% in comparison with state 2.
In states 2 and 3 ductility of the material is about 3 – 4 % at 300 and 77 К. Fracture at 4.2 К
took place without macroscopic plastic deformation under σ~ 1.5-1.6 GPа, that corresponds to
the yield stress in the initial state at 4.2 К. Observed differences in the strength and ductility
characteristics of the Ti-6Al-4V ELI alloy, apparently, dependent on additional barriers for
dislocations motion in the 2 and 3 states: these are twins colonies (state 2) and additional
grain boundaries, which number increases essentially in the ultrafinegrained state 3 and (in a
lesser degree) in the state 2. Values of activation volume V for dislocations motion, obtained
from a stress relaxation data, are practically independent on the alloy structural state. Thus, at
281
the yield stress at 300 K and 77 К V ≈ 3.5x10-28 m3 and V ≈ 0.9x10-28 m3, correspondingly.
SEM fractographic analysis of the fracture surfaces of the ultrafinegrained Ti-6Al4V ELI
specimens shows that at 300, 77 and 4.2 К ductile failure takes place at the microscale.
[1] I. P. Semenova, L. R. Saitova, G. I. Raab, A. I. Korshunov, Y. T. Zhu, T. C. Lowe, R.Z.
Valiev, Material Science Forum, 503-504 (2006) 757
282
BNM-2007, 17 August, Poster Session C Poster report
Severely Cold-Rolled and Annealed Ti-Ni Shape Memory Alloys: Structure, Transformations and Functional Properties
Sergey Prokoshkina,1, Vladimir Brailovskib,2, Karine Inaekyana, Vincent Demersb,
Irina Khmelevskayaa, Sergey Dobatkinc and Evgeniy Tatyanind
a Moscow State Institute of Steel and Alloys, 4 Leninskiy Pr., Moscow 119049 Russia b Ecole de Technologie Superieure, 1100 Notre-Dame Ouest, Montreal (Quebec) H3C 1K3, Canada
c Baikov Institute of Metallurgy and Material Science of RAS, 49 Leninskiy Pr., Moscow 119049 Russia d Institute for High Pressure Physics of RAS, Troitsk, Russia
In recent years, Zn-Al alloys have emerged as a potential cost- and energy-effective, and
environmentally friendly system for substituting several ferrous and non-ferrous alloys in
various engineering applications. However, their low strength, very poor ductility and low
impact toughness limit the use of these alloys. Some traditional methods like alloying, heat
treatment and composite forming have been used; however, the resulting improvements in
these properties have not been satisfactory. In this study, the effect of equal-channel angular
extrusion (ECAE) processing at 130°C on tensile properties and impact toughness of two-
phase Zn-40Al alloy were investigated for up to four passes via route BC in order to improve
their inferior properties. Fracture behaviors of processed and un-processed alloy after tensile
and impact tests were also examined. As a result of multi-pass ECAE, elongation to failure
increased significantly with increasing the number of ECAE passes as shown in Fig.1(a). The
sample extruded 4 passes exhibited 88% elongation to failure at room temperature, which
were 13 times higher than that of the as-cast alloy. The ECAE also increased the strength of
the alloy after one pass, however, higher number of passes led to drop in the strength
(Fig.1(a)). Moreover, the impact toughness of the alloy was improved by multi-pass ECAE
due to the increased ductility as well as smaller fracture dimples as shown in Fig.1(b). By
means of multi-pass ECAE, Zn-40Al casting alloy having brittle fracture behavior were
transformed into the tougher alloy having typically ductile fracture behavior as shown in
Fig.2. These results indicate that the multi-pass ECAE is effective in improving the tensile
elongation and impact toughness of binary Zn-Al alloys.
285
Number of passes0 1 2 4
Stre
ngth
(MP
a)
100
150
200
250
300
350
Elo
ngat
ion
to fa
ilure
(%)
20
40
60
80
100
Tensile strengthYield strengthElongation to failure
Number of passes0 1 2 3 4
Impa
ct to
ughn
ess
(kg.
cm/c
m2 )
40
60
80
100
120
140
a b
Figure 1. The effect of multipass-ECAE on (a) strength and elongation to failure, and (b) impact toughness of Zn-40Al alloy
Figure 2. Appearance of the failed tensile specimens and their fractured surfaces. a) As-cast (0 P), b) one pass
(1 P), c) two passes (2 P) and d) four passes (4 P)
286
BNM-2007, 17 August, Poster Session C Poster report
Dissipation and Deposition Discontinuous Harden Particles in Cu-1Cr-0.7Al-0.2Zr Alloy by ECAP
Svetlana N. Faizova1, Vladimir V. Latysh2, Valery N. Danilenko4, Elena A.
Sarkeeva3,a and Irek V. Kandarov2 1 Instititute of Mechanics, Ufa Science Center, Russian Academy of Sciences,
71 Oktyabr Pr., Ufa 450001 Russia 2 Designing Technological Bureau “Iskra”, 81 Pushkin St., Ufa 450000 Russia 3 Ufa State Aviation Technical University, 12 K. Marx St., Ufa 450000 Russia
4 Institute for Metals Superplasticity Problems, 39 Khalturin St., Ufa 450001 Russia a [email protected]
Chromium bronzes are a special class of high-copper alloys combining in their properties high
electrical conductivity with high strength what makes them attractive for many industrial
applications. Chromium bronzes of the Cu-Cr-Zr system are the precipitation hardening
alloys. The optimal composition of physical and mechanical properties for these materials
may be reached through the specific combination of mechanical and thermal treatments.
Using the severe plastic deformation (SPD) methods, particularly the multi-pass equal
channel angular pressing (ECAP), with the appropriate thermal treatment it is possible to
significantly increase the strength of the materials while preserving the high electrical
conductivity.
In the present work the influence of the solid solution treatment and the SPD parameters on
the dissolution and precipitation of alloying elements in Cu-1%Cr-0.7%Zr alloy has been
studied. The chemical composition, the morphology and the size distribution of the
precipitation particles have been studied using the extraction replicas technique.
The solid solution treatment of the commercial alloy samples was carried out at 1050°C for 5
and 10 hours. It has been found that the degree of dissolution and, correspondingly, the size
distribution of the remaining particles are different for these treatment durations. The size
distribution of the particles had the bi-modal form. The microhardness values were 510 MPa
and 670 MPa for 5 and 10 hrs, correspondingly, what well correlated with structural
differences.
The analysis of the structural changes demonstrated that the SPD (8 passes of the ECAP along
the Bc route) activates the diffusion what results in the stain-induced decay of the solid
solution prepared at the previous stage. The average size of the remaining particles
significantly decreased and became approximately equal for both treatment times. This result
287
may also be considered as the evidence for the strain-induced diffusion enhancement during
the SPD.
The ECAP resulted in the structure refining of the material to the sub-micrometer scale. The
microhardness values after the SPD were 1670 MPa and 1670MPa for 5 and 10 hrs,
correspondingly.
This work was supported by RFBR grant (projects No. 06-08-00971, 07-08-00567-а).
288
BNM-2007, 17 August, Poster Session C Poster report
Bulk Nanostructured Materials: Pathways for Commercialization Andrey Shcherbakova,1
a Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, 12 K. Marx St., Ufa 450000 Russia
For the purpose of evaluating the strategy of creating the implant materials it is advantageous
to investigate the topological rules of
the compositions diagrams. The
investigation of this kind lies in the
fact that the composition of the
complex compounds is at the
intersection of the secants connecting
the binary phases tops in the
compositions polyhedron as it was
made for the multicomponent system
of Collagen– CaO – P205 – H2O
(Fig.1). This fact has made it
possible to reveal the identification
region of the nanocrystalline
compound material LitAr used for
filling the defects of the bone and parenchymatous tissues [1].
This compound material is a high integrated system of collagen fibers with nanocrystalline
hydroxyapatite. The problem of conformity of the present material with the native bone has
been successfully solved with the help of analyzing the diagram on which the composition
region (hydroxyapatite HA, enamel, LitAr, bone, blood cell, blood) (Fig.2) has been
distinguished.
The condition which determines the biological activity of the material is nanometricity (Fig.3)
of its salt component [2]. This fact ensures universality of the material stimulating the
patient`s stem cells [3].
CaO
Collagen
HA
P O2 5
H O2
H P O4 2 7
H PO3 4
HPO3
H[P O ]3 81:3
2:13:1
1:1
mol.%
HA region
5:1 10:31:1
Ca(OH)2
1:1
HA
Са5[P O ]2 10Ca(PO )3 2
Ca P O2 2 7
2:1
Са10 6 25[P O ]Ca (PO )3 4 2
3:1
Figure 1. The diagram of the compositions of the 4-component system Collagen – CaO – P205 – H2O
290
The application of the topological choosing
criterions will make it possible to determine the
promising region of synthesis of the new
nanometric compound materials of the medical
purpose.
[1] S.D. Litvinov, I.I. Markov, M.M.
Olennikova, Biomaterialien, 3 7 (2006) 186
[2] S.D. Litvinov, T.V. Sudakova, A.S.
Seryogin. Book of Abstracts of Topical
Meeting of the European Ceramic Society
"Structural Chemistry of Partially Ordered
Systems, Nanoparticles and
Nanocomposites". Saint-Petersburg, Russia
(2006) 162
[3] S.D. Litvinov, I.I. Markov, T.V. Sudakova.
Proceedings of International Conference
“Chemistry, Chemical Engineering and
Biotechnology”. Tomsk: TPU, 2 (2006)
395
HA
H O2
enamel
bone
plasma
bloodcell
LitAr
Figure 2. The compositions plane
Figure 3. The hydroxyapatite nanocrystals in the material LitAr
291
BNM-2007, 17 August, Poster Session C Poster report
Modeling of Isothermal Forging of Compressor Blade Made of Nanostructured Ti-6Al-4V Alloy
Alexander V. Botkina,1, Azat F. Shayahmetova,2, Alexander A. Kuzminyha,3 a Institute of Physics of Advanced materials and Nanotechnology Department, Ufa State Aviation
On an example of carbon - carbon system the opportunity of realization the monostage
technology nanocomposits for engineering industry is shown.
Considering graphite as a limiting degree of condensation of aromatic hydrocarbons have
estimated a critical diameter it nanoparticles .For carbon in allotropic modification of graphite
that make up about 10 nm. The many years research of a representative samples of industrial
batches of nanocomposite has shown the satisfactory compliance of experimental value of
d cr.(9.2 nm) of graphite with the theoretical data.
Nanoparticles of carbon and carbon matrix, connecting them, are formed in uniform
technological process simultaneously. The industrial technology of the nanocomposite as
plates and tubular pieces, and also as specific articles with the size up to 200 mm and the wall
thickness up to 10 mm is developed during the practical production processes.
Structure and basic properties the nanocomposite of carbon–carbon systems compliance with
the theoretical data. The carbon nanocomposite has a unique combination of properties: it is
chemically and biologically inert, air and liquid impermeable, radiation resistant and
surpasses any carbon materials: in friction coefficient 5 times, in cathode sputtering
coefficient 15 times, in oxidizing resistance up to 300 times and surpasses tungsten in high-
temperature specific durability. The above properties ensure functioning capability of
advanced machines and devices.
The offered approach to solution of technological problems of nanomaterials can be used in
creation of one-stage technology nanosystems of a filler-matrix of other chemical
composition.
296
BNM-2007, 17 August, Poster Session C Poster report
Brittle-Ductile Transition in Commercial Pure Tungsten with Ultrafine-Grained Microstructure
Yue Zhanga,1, Jing Tao Wanga,2 J.Q.Liua,3, Artur Ganeevb,4 and Igor V.Alexandrovb,4 a School of Materials Science and Engineering, Nanjing University of Science and Technology,
Nanjing, Jiangsu 210094, P. R. China b Institute of Physics of Advanced Materials, Ufa state Aviation Technical University,