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Improving Aluminum Casting Alloy and Process Competitiveness A. Mandal and Makhlouf M. Makhlouf
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Improving Aluminum Casting Alloy and Process Competitiveness
A. Mandal and Makhlouf M. Makhlouf
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Project Objectives
The objective of this project is to obtain a new family of
aluminum-silicon alloys that can be processed by high-
pressure die-casting at significantly lower than usual
temperatures and therefore is cost-effective; and that is heat-
treatable, and therefore is capable of significantly higher
ductility, with no sacrifice in other mechanical properties.
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Strategy
Phase 1 Developing a new family of aluminum-silicon alloys that is castable at significantly lower than usual temperatures.
Development of an optimum heat treatment schedule for the new alloy system.
Phase 2 Die-casting of the alloy system developed in Phase 1 at sufficiently low temperatures which will cause negligible soldering of the alloy to the die.
Phase 3 Exploring the possibility of heat-treating die cast samples.
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Background
Effect of Mg on Al-10Si alloy
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Effect of Mg on Al-14Si alloy
6
Variation of Eutectic point
0 1 2 3 412.6
12.8
13.0
13.2
13.4
13.6
560
564
568
572
576
wt% Mg
Eute
ctic
Si,
wt.%
Eute
ctic
Tem
pera
ture
, o C
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Effect of cooling rate – Cast Iron Mold(220oC/min)
3 wt% Mg2 wt% MgAl-14Si alloy
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Effect of cooling rate – Copper Mold(300oC/min)
3 wt% Mg2 wt% MgAl-14Si alloy
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Average Size of Mg2Si
2.0 2.5 3.00
20406080
100120140160180200
Size
of M
g 2Si, µ
m
w t% Mg
Sand Cast (45oC/min) Cast Iron Mold (220oC/min) Copper Mold (300oC/min)
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Modifiers used for the modification of Mg2Si particles
0.2, 0.5, 1 wt%Calcium
0.02, 0.05, 0.2, 0.5 wt%Phosphorus
0.025, 0.050, 0.5, 1 wt%Strontium
0.25, 0.50, 0.75, 1 wt% Cerium
0.25, 0.50, 0.75, 1 wt%Yttrium
Addition level
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Effect of Yttrium
1 wt%0.75 wt%0.5 wt%
0.50 0.75 1.00160
165
170
175
180
185
Part
icle
siz
e of
Mg 2S
i, µm
wt% Y
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Effect of Cerium0.25 wt% 0.50 wt%
0.75 wt% 1.00 wt%
Mg2Si
Si
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0.00 0.25 0.50 0.75 1.0020
40
60
80
100
120
140
160
180Pa
rtic
le s
ize
of M
g 2Si, µ
m
wt% Ce
Average size of Mg2Si
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Effect of Strontium0.050 wt%
0.50 wt% 1.00 wt%
0.025 wt%
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Modified morphology of Mg2Si
0.0 0.5 1.045
50
55
60
65
70
Part
icle
siz
e of
Mg 2S
i, µm
wt% Sr
16
0.25 Ce + 0.050 Sr0.25 Ce + 0.025 Sr
Combined Effect of Ce and Sr
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SEM MicrographWith additionWithout addition
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Al-14Si-3Mg treated with0.25Ce + 0.025Sr
T6 – 4 hT4 – 1 dayas cast
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Mg2Si
Mg2Si
Eutectic Si
SEM Microstructures
T6 – 4 hT4 – 1 dayas cast
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300.51.041.143.8After 8 h
305.90.942.845.5After 4 hT6
367.34.426.039.2After 10 days
331.04.024.435.0After 1 dayT4
273.42.719.430.4-As cast
QI*(MPa)
%ElYS(ksi)
UTS(ksi)
0.25Ce + 0.025SrHeat TreatmentCondition#
Temper
Tensile Properties
* QI Ξ Quality Index = UTS (MPa) + 150 log [% El.]# Solution Treatment: 520oC for 12 h
Ageing Temperature: 200oC for 4 h & 8 h
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Effect of Phosphorus0.05 wt%
0.20 wt% 0.50 wt%
0.02 wt%
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0.1 0.2 0.3 0.4 0.580
100
120
140
160Pa
rtic
le s
ize
of M
g 2Si, µ
m
wt% P
Average size of Mg2Si
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Ca rich phase
Effect of Calcium
1 wt%0.5 wt%0.2 wt%
0 .2 0 .3 0 .4 0 .5 0 .6 0 .7 0 .8 0 .9 1 .0
6 0
8 0
1 0 0
1 2 0
1 4 0
1 6 0
Part
icle
siz
e of
Mg 2Si
, µm
w t% C a
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293.90.744.746.0After 8 h
276.30.840.542.2After 4 hT6
After 10 days
318.62.526.537.5After 1 dayT4
194.21.120.526.9-As cast
QI*(MPa)
%El.YS(ksi)
UTS(ksi)
0.5 wt% CaHeat TreatmentCondition#
Temper
Tensile Properties
* QI Ξ Quality Index = UTS (MPa) + 150 log [% El.]# Solution Treatment: 520oC for 12 h
Ageing Temperature: 200oC for 4 h & 8 h
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Isopleths of Al-14Si-3Mg-xCu alloys
Θ = Al2Cu
Q = Al5Cu2Mg8Si6
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% Phases inAl-14Si-3Mg-xCu alloys
0 1 2 3 4 5 60123456789
1 0
a t e le v a te d te m p e ra tu re
A l2C u
M g 2S i
M g 2S i
A l5C u 2M g 8S i6
Con
stitu
ent (
wt.%
)
C u (w t.% )
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As Cast Microstructure – Sand mold(45oC/min)
Q phaseSi
Al2Cu
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Effect of Solutionising Times at 480oC
36 h24 h12 h
Q phase Q phase
Q phase
fragmentationspheroidisationno change
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As cast ST = 12 h ST = 24 h ST = 36 h
8
10
12
14
16
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Size
of Q
pha
se, µ
m
Heat Treatment Condition
Average size of Q phase
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Summary
Hypereutectic Al-14Si-3Mg-0.2Fe alloys with Yttrium, Cerium, Strontium, Phosphorus and Calcium addition was tried out with a view to modify the Mg2Si particles. One of the alloys showed an elongation of 4.4% (T4 condition) and a tensile strength of 46 ksi (T6 condition).
The scope of Cu addition to Al-14Si-3Mg alloy was assessed and results indicated that spheroidisation of Q phase was possible for higher solutionising times.
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Deadlines for the Project
December 2008Phase III
June 2008Phase II
December 2007Phase I
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