ENCYCLOPÉDIE DE LA RECHERCHE SUR L’ALUMINIUM AU QUÉBEC 2013 | Page 48
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NOUVEAUX PRODUITS ET MATÉRIAUX À BASE D'ALUMINIUM
NEW ALUMINIUM BASED PRODUCTS AND MATERIALS
EFFETS DU Zr ET Sc SUR LES PROPRIÉTÉS MÉCANIQUES DES ALLIAGES D’ALUMINIUM
DE TYPE Al-2%Cu COULÉS PAR LA TECHNIQUE DE MOULAGE SOUS BASSE PRESSION
EFFECTS OF Zr AND Sc ADDITIONS ON THE TENSILE PROPERTIES
OF Al-2%Cu BASED ALLOYS PRODUCED BY LPDC TECHNIQUE
G.A. Zaki,1 A.M. Samuel,1H.W. Doty,2 F.H. Samuel
1
Université du Québec à Chicoutimi, Chicoutimi, Québec, Canada, G7H 2B1
2General Motors, Materials Engineering, 823 Joslyn Avenue, Pontiac, MI 48340, USA
1
2
1. Introduction
Over the years, aluminum-copper cast alloys have been increasingly investigated, the reason being that copper has a significant impact on the strength and hardness of
aluminum castings at both ambient and elevated service temperatures. Due to the presence of copper, the mechanical properties of these alloys may be improved through
age hardening. Copper also improves the machinability of such alloys by increasing the matrix hardness, making it easier to generate small cutting chips and fine machined
finishes.
Additions of Zr and Sc to Al alloys have been reported to preserve the mechanical properties at high temperatures, through the precipitation of Al 3Zr and Al3Sc
dispersoids which maintain their strength at elevated temperatures.
In the present work, the tensile properties of Al-2%Cu based alloys containing Zr and Sc additions were investigated. Castings were made using the low pressure die
casting (LPDC) technique which provides several advantages including high productivity, control of process parameters, and reduced machining costs.
2. Objectives
2
1
Investigate and understand the performance
of Al-2%Cu based alloys produced by the
low pressure die casting technique.
3
Examine the microstructures of the various alloys
prepared to determine the phases and precipitates
obtained in as-cast and T6 heat-treated conditions.
Determine the tensile properties & analyze data obtained in terms of
the effects of alloying additions & heat treatment parameters on the
UTS, YS and %El values, employing mathematical analysis.
3. Experimental Procedures
List of Al-2%Cu Based Alloys Prepared for this Study
Alloys
Code
Alloy
220A
220 - Base Alloy : Al-2%Cu-1.32%Si0.42%Mg-0.58%Fe-0.59%Mn-0.07%Ti
No. of Tensile Bars
100
220B
A + 0.02%Sr
100
220C
A + 0.15%Ti
100
220D
A + 0.15%Ti +0.02%Sr
100
220E
A + 0.15%Ti + 0,50%Zr
100
220F
A + 0.15%Ti + 0,30%Zr
Tensile test bar castings were prepared using the LPDC technique. One hundred test bars were cast per alloy composition. In this technique, the
permanent die and the filling system are placed over the furnace containing the molten alloy. The cavity is filled by forcing (using pressurized gas @ 0.3 to
1.5 bar) the molten metal to rise into a ceramic tube which connects the die to the furnace. Once the die cavity is filled, the overpressure in the furnace is
removed, and the residual molten metal in the tube flows again into the furnace. The various parts of the die are then separated, and the casting is extracted.
T6 heat treatment was carried out as follows: a) solution heat treatment at 490C for 8 hrs, followed by b) quenching in warm water, and then c) artificial
aging at temperatures of 155, 180, 200, 220, 240 and 300C for 5 hrs at each temperature.
The test bars were tested at room temperature in the as-cast and T6 heat-treated conditions using an MTS Servohydraulic Mechanical Testing Machine,
at a strain rate of 2 x 10-4/s.
Low Pressure Die Casting
Machine
Mold Used for Casting
LPDC Casting
100
220G
A + 0.15%Ti + 0.50%Zr + 0.70%Ag
100
220H
A + 0.15%Ti + 0.02%Sr + 0.50%Zr
100
220I
A + 0,15%Ti + 0.02%Sr + 0.50%Zr + 0.70%Ag
100
220J
A + 0.15%Ti + 0.30%Zr + 0.15%Sc
100
220K
A +0.15%Zr
100
220L
A +0.30 %Zr
100
220M
A +0.50 % Zr
100
4. Results
Gergis A. Zaki
Agnès-Marie Samuel
Fawzy Hosny Samuel
Université du Québec
à Chicoutimi
As-Cast
SHT
Aging-220 C
Grain Size and Microstructure
Aging-300 C
Total volume fraction of intermetallics observed in cast 220 alloys
A
B
C
D
E
F
G
H
I
J
4.44
4.71
4.44
3.59
6.32
5.78
3.87
5.34
4.23
5.89
Std Dev
UTS
Herbert W. Doty
General Motors,
Materials Engineering
Alloy
Average
0.34
0.62
0.20
0.43
0.84
0.97
0.45
0.50
0.76
0.53
Alloy A (As-Cast)
Grain size at a) low, &
b) high magnification;
and c) microstructure
a)
b)
c)
a)
b)
c)
YS
Alloy I (As-Cast)
Grain size at a) low, &
b) high magnification;
and c) microstructure
Al3Zr
5. Conclusions
Elongation (%)
Addition of Zirconium leads to significant improvement in mechanical
properties in both as-cast & heat-treated conditions, due to its grain refining
action; fine coherent Al3Zr dispersoids are observed in the microstructure.
Aging at 220C provides best comprise between strength & ductility overall.
Aging at 300C results in softening, and a corresponding increase the
ductility, however at the expense of strength.
Journée des étudiants – REGAL
Aluminum-copper alloys have been extensively investigated over the years,
Les alliages de type Al-Cu ont été largement étudiés depuis plusieurs années.
Palais des congrès de Montréal, QC, Canada, 22 octobre 2013
where the presence of Cu allows for improving the alloy mechanical properties
La présence du Cu permet d’améliorer les propriétés mécaniques de ce type
through the formation of Al3Cu precipitates via age hardening. Additions of Zr
d’alliage par durcissement, à travers la formation des précipités de Al3Cu au cours
d’un traitement thermique. L’a jout du Zr et du Sc à ces alliages préserve leurs
and Sc to Al alloys have been reported to preserve the mechanical properties
propriétés à haute température, en raison de la formation des précipités Al3Zr et
at high temperatures, through the precipitation of Al3Zr and Al3Sc dispersoid