In this paper we present some results concerning plastic deformation applied to shape memory alloy and two most direct characterization methods for shape memory. We work with a copper based alloy- Cu Al13Ni 4. Over eight percent in aluminum the plastic deformation on the copper aluminum alloys is very difficult to do. Our purpose was to obtain the thin wires. The first material shape was cast ingots very fragile. We choose to work with a direct extrusion method because the high fragility of this material required a three dimensional stress compression scheme

Carmela GURAU

Gheorghe GURAU

The Annals of “Dunarea de Jos” University of Galati Fascicle IX Metallurgy and Materials Science

Directory of Open Access Journals

 
THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
0FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. N . 1 – 2006 
 
 
 
PROCESSING SMART WIRES FROM CU-AL-NI SYSTEM 
 
Carmela GURAU, Gheorghe GURAU 
Dunărea de Jos” University of Galati 
e-mail: carmela.gurau@ugal.ro
 
ABSTRACT 
 
In this paper we present some results concerning plastic deformation applied 
to shape memory alloy and two most direct characterization methods for shape 
memory. We work with a copper based alloy- Cu Al13Ni 4. Over eight percent in 
aluminum the plastic deformation on the copper aluminum alloys is very difficult to 
do. Our purpose was to obtain the thin wires. The first material shape was cast 
ingots very fragile. We choose to work with a direct extrusion method because the 
high fragility of this material required a three dimensional stress compression 
scheme.  
 
KEYWORDS: smart memory alloy, extrusion 
 
 
 
1. Introduction 
 
The motivation for this research is the market 
requirement for a new materials class Shape Memory 
Alloy (SMA). This materials are expensive because 
use the expense elements also use expense 
technologies. In these conditions our purpose was to 
choose an easy obtain smart material and to find 
adequate processing. We chose the copper based 
SMA using the former team experience in cooper 
alloys [1], [2], [5]. 
Shape Memory Alloys is a designation that is 
applied to that group of metallic materials that 
demonstrate the ability to return to some previously 
defined shape or size when subjected to the 
appropriate thermal procedure. Generally, these 
materials can be plastically deformed at some 
relatively low temperature, and upon exposure to 
some higher temperature will return to their shape 
prior to the deformation. 
A shape memory alloy may be further defined 
as one that yields a thermoelastic martensite. 
In this case, the alloy undergoes a martensitic 
transformation of a type that allows the alloy to be 
deformed by a twinning mechanism below the 
transformation temperature.  
The deformation is then reversed when the 
twinned structure reverts upon heating to the parent 
phase. [6] 
 
2. Melting conditions 
 
The melting process has been developed in a 
tipping furnace graphite melting pot. The maximum 
charge weight: 100 kg. For the charge composition 
we used electrolytic copper plates, nickel and 
titanium plates. 
Practically in burning melting pot was 
introduced protection material. When this material 
came incandescent the electrolytic cooper preheated 
at 200 0C was introduced.  
The method supposes ingot casting followed 
melting to avoid pre alloys for purity reasons. At 
same time we had a special attention for melting bath 
protection. In this way we used Na2BB4O7 and NaCl. 
Deoxidation was made with CuP10 and degasification 
with Cl2Mn.  
The melting scheme is: 
 
 
 
 
 
 
 
 
 
Cu
CuE             Ni           CuE      Al   alloy   re melting             
 alloy 
P10 
CuP10 
First 
Deoxidation 
Second 
Deoxidation
Stop Furnace  
Casting Ingot Casting samples 
-  49  -
The melting conditions were managed so that 
cooper fusion to be faster. Final temperature was 
11500C. In this moment was made a first deoxidation 
with CuP10. Nickel also pre heated was added in small 
parts. In this time a bath agitation was made. From 
initial weight 10% was retained and is used in this 
moment for reduce the bath temperature. 
This reduce is necessary for aluminum addition. 
The second deoxidation followed.  
The chemical composition was determined 
using a Qantovac device based on the optical spectral 
analysis. The result is presented in table 1.  
The structure for this alloy (fig.1) and a classic 
bronze microstructure are very different. 
 
 
 
Fig.1. Alloy with 13%Al and 4% Ni, 
Alloy: Cast aluminium bronze 
Chemical composition: 13 %Al, 4 Ni, rest Cu 
Magnification: 50x 
 
 
Fig.2. Stress scheme direct extrusion 
 
3. Plastic Deformation 
 
Before the plastic deformation technology was 
choose necessary behavior plastic deformation study 
was made [1], [2], [4]. All those study confirm that 
upper 10% Al plastic properties of alloy are 
pronounced decrease. 
In these conditions direct hot extrusion process 
was designed. This deformation process must resolve 
problem to obtain cylindrical shapes 10 mm diameter 
and 120 mm length starting from normal conic 
molded ingot (Φ25-Φ40)x 150 mm, aluminum bronze 
4%Ni.  
 
 
Fig.3. Direct extrusion die 
 
The direct extrusion is only plastic deformation 
method which assures tri dimensional compressive 
stress (fig. 2) indicates for such hard deformable 
alloy.   
In this sense was designed a direct extrusion 
dies (fig. 3) to assure plastic deformation from 35 mm 
diameter to 3mm diameter wires (fig. 4). The 13 % Al 
extruded semi products microstructure show a 
martensitic aspect (fig. 5). 
 
 
 
 
Fig.4. A- ingot, B- 20 mm extruded shape, C-10 
mm extruded shape 
 
alloy 1 
Nr.crt Sn Pb Zn Mn Fe Ni Si Al Cu 
4.1 0.02 0.01 0.79 0.09 0.27 4.00 0.04 12.88 Rest 
-  50  -
 
THE ANNALS OF “DUNAREA DE JOS” UNIVERSITY OF GALATI 
0FASCICLE IX METALLURGY AND MATERIALS SCIENCE, ISSN 1453 – 083X. N . 1 – 2006 
 
 
 
Smart memory alloy deformation degree 111% 
Chemical composition 12.88%Al, 3.84% Ni, rest Cu 
Microstructure: γ1′ 
Magnification: 100x 
Smart memory alloy deformation degree 111% 
Chemical composition 12.88%Al, 3.84% Ni, rest Cu 
Microstructure: γ1′ 
Magnification: 100x 
  
Fig. 5. Microstructure 13% Al smart memory alloy 
 
The last plastic deformation was made from 10 
mm diameter to 3 mm wires.  
In figure 6 is presented the semi product and the 
extrusion dies. 
 
 
Fig.6. Extrusion die, punch, 3 mm extruded wire 
 
 
Fig.7. Extruded SMA wires 
 
Our next step study has been concentrated on 
aged and quenched specimens of Cu-Al-Ni alloy, 
solubilized and we performed, the Differential 
Scanning Calorimetry and Electrical Resistivity 
characterization techniques. 
The specimens were solubilized in austenitic 
domain at 850°C for 30 minutes. Homogenized 
specimens were immediately quenched in iced water 
in order to obtain β-type martensite. 
 After these treatments the calorimetric 
experiments were performed by means of SETARAM 
92 instrument at a rate of 10°C per minute, between -
50°C and 250°C. The cooling treatments were acted 
by using liquid nitrogen. The electrical resistivity to 
identify the crystalline phases present in materials and 
to measure the structure properties was made with a 
THERMO ELECTRON COOP HAAKE DC50-K40 
 
4. Characterization methods 
 
There are two major methods of characterizing 
the transformation in SMAs and a large number of 
minor methods: 
Differential Scanning Calorimetry 
Electrical resistivity 
The objective of the present work is to analyze 
the variation of the temperature with thermal cycling 
using the Differential Scanning Calorimetry (DSC), 
and the electrical resistivity to identify the crystalline 
phases present in materials and to measure the 
structure properties.  
The most direct method is by DSC. This 
technique measures the heat absorbed or given off by 
a small sample of the material as it is heated and 
cooled through the transformation temperature range. 
The sample can be very small, such as a few 
milligrams, and because the sample is unstressed, this 
is not a factor in the measurement. The endotherm 
and exotherm peaks as the sample absorbs or gives 
off energy due to the transformation, are easily 
measured for the beginning peak, and end of the 
phase change in each direction. 
-  51  -
 
Fig.8. DSC SETARAM 92 
 
The se easure the 
electrical resistivity of the sample as it is heated and 
coole
ir mechanical, electrical or 
magn
5. Experimental results 
A sample w was cut from a 
Cu-Al-Ni wire, etched with solution of 1:1 HNO  
and H
cond method often used is to m
d. The alloys exhibit interesting changes and 
peaks in the resistivity (by up to 20%) over the 
transformation temperature range; however, 
correlating these changes with measured phase 
changes or mechanical properties has not always been 
very successful. Also, there are often large changes in 
the resistivity curves after cycling samples through 
the transformation a number of times. Thus, 
resistivity is often measured as a phenomenon in its 
own right, but is rarely used to definitely characterize 
one alloy versus another. 
The technical importance of most engineering 
materials is based on the
etic properties, which should, normally, be as 
independent as possible from environmental 
influences. 
 
DSC analysis 
 
eighting 0.0347g 
a 3
2O for 13 minutes to remove the layers affected 
by the cutting. The calorimetric experiments were 
performed between -50°C and 250°C at a heating rate 
of 10°C/min. The cooling treatments were carried out 
by using liquid nitrogen. 
 
 
Fig.9.  
 
The curve from (f  a closed one with no 
phase transformation, with no peak on the reverse 
marte
on forward and reverse direct 
marte
ig 9) was
nsite transformation, between 73°C and 159°C 
present a large peak. 
The quenched curves (fig.10) showed a phase 
transformation both 
nsitic transformation. 
 
50 100 150
50
100
Cooling
2
1
50 100 150
-150
-100
-50
Flo
w
(m
W
/g)
Temperature (ºC)
Heating
1
2
 
Fig.10. DSC curves for a solubilized alloy at 
850ºC 
6. ER analyses 
We can obs the resistivity is 
increasing with the temperature rising, showing that 
there
 
 
 
erve a straight line, 
 is no phase transformation at the 9 months aged 
at room temperature specimen. 
 
20 40 60 80 100 120 140
9.2
9.4
9.6
9.8
10.0
10.2
10.4
10.6
10.8
11.0
CuAlNi
Aged for 9months at RT
Dt.23-03-2006
 
 
R
es
is
tiv
ity
 (m
ic
ro
O
hm
-c
m
)
Temperature (oC)
 
Fig11. ER aged sample 
 
-  52  -
At 850°C solubilised sample there is a phase 
transformation that starts around 85°C, the resistivity 
starts to decrease until 103°C when the phase is 
finished and the resistivity has the tendency to 
increase. On cooling a reverse phase transformation 
takes place. 
 
0 20 40 60 80 100 120 140
10.0
10.5
11.0
11.5
12.0
12.5
CuAlNi
Annealed at 850degC
Dt.23-03-2006
 
 
R
es
is
tiv
ity
 (m
ic
O
hm
-c
m
)
Temperature (C)
 
Fig.12. ER quenched sample 
 
 table 2 we have transformation temperatures 
obtai
Table 2 
lubilized at 
In
ned from DSC and ER measurements. 
 
So
850ºC Transformatio
DSC ER 
n 
temperatures 
As 92 80 
Af 138 103 
Ms 152 90 
Mf 84 60 
 
7. Conclusions 
The extruded wires h ve a martensitic structure 
to th
e shape memory effect.  
 transformations that are 
typic
wledgement 
The aut e the 
support from CENIMA  FCT/UNL Caparica, 
Portug
rences 
[1]. Gheorghe,G., Teza rsitatea Dunarea de Jos 
alati 
y 
 
a
e normal temperature. Dimensions and micro 
structural aspect allow continuing to the next step 
establishing thermo mechanical treatments to induce 
The Cu-Al-Ni, after solubilization followed by 
quenching, showed the phase
al of the Shape Memory Effect (by DSC and 
Electrical Resistivity). 
 
Ackno
 
hors would like to acknowledg
T
al, specially Mister Professor F.M. Braz 
Fernandes and his team. 
 
Refe
 
 de doctorat, Unive
G
[2]. Cănănău,N., Teza de doctorat, Universitatea Dunarea de Jos 
Galati 
[3]. Cananau, N, Gurau, G., Comportarea la deformare a 
materialelor metalice. Ecuatii constitutive, Editura Evrika, 1996 
[4]. Cănănău, N, Mitoşeriu, O., Researches concerning the heat 
treatment at special aluminium bronze for shiping propellers, 
Euromat, Lisabona, Portugalia, 1998, vol.2, pag.293-298 
[5]. Vlad, M., Teza de doctorat, Universitatea Dunarea de Jos 
Galati 
[6]. Darel Hudgson, Ming H.Wu and Robert J. Biermann 
“Shape memory alloys for power connector apllications” 
Z[7]. .G. Wei’ H.Y. Peng; D.Z.Yang\ C.Y Chung and J.K.L.Lai 
“Reverse transformations in CuAlNiMnTi alloy at elevated 
temperatures” 
[8].  G.M Loughran; T.W Shield, P.H Leo “Fracture of shape 
memory CuAlNi single crystals” 
[9]. V.Recarte; J.I. Perez- landazabal, A. Ibarra, M.L. No “ 
High temperature β phase decomposition process in Cu-Al-Ni 
SMA” 
[10]. J.Font, E,Cesari, J. Muntasell, J.Pons “ Thermomechanical 
cycling in Cu-Al-Ni-based melt-spun shape memory ribbons” 
[11]. R.Gastien, C.E.Corbellani, M.Sade “ Thermomechanical 
aspects of martensitic transformations in CuAlNi single crystals”   
[12].  Ganesh Ganapardy, Abhijit Bhattacharyya “The effect onf 
isothermal mechanical cycling on Cu-Al-Ni shapememory alloy 
single crystal wire” 
[13]. K.Otsuka and C.M. Wayman “ Shape memory materials” 
[14]. J.Gui, W.H.Zon, D.Zang “ X-RAY diffraction study of the 
reverse martensitic transformation in Cu-Al-Ni-Ti shape memor
alloy” 
[15]. A.S. Paula, J.P.H.G. Canejo, R.M.S. Martins, F.M. Braz 
Fernandes “ Effect of thermal cycling on the transformation 
temperature ranges of Ni-Ti shape memory alloy”. 
th
 
-  53  -


Processing Smart Wires from Cu-Al-Ni System

https://www.gup.ugal.ro/ugaljournals/index.php/mms/article/download/3227/2907

Processing Smart Wires from Cu-Al-Ni System

Abstract

Similar works

Full text

Available Versions

Directory of Open Access Journals