Advances in Precision Sand Casting of Aluminum Engine ... - AUTO21

Advances in Precision Sand Casting of
Aluminum Engine Blocks
Dr. Robert Ian Mackay,
Nemak of Canada Corporation
Dr. Jerry Sokolowski,
University of Windsor
June 03, 2008

Agenda
•The Problem: Durability of Aluminum Cast Engine Blocks
•Casting Methods To Address Bulkhead Integrity
•Alloy Chemistries: Subject of Research
•Testing Analysis & Results
– ASTM 466-6
– Staircase Fatigue Testing
2

Bulkhead Cyclic Loads
LLT CA vs Bulkhead loads
bulkhead loads
45000
40000
35000
30000
25000
20000
15000
10000
5000
Series5
Series2
Series3
Series4
0
0 100 200 300 400 500 600 700 800
crank angle

Fatigue Damage in Bulkhead Sections

Casting Methods To Address Bulkhead Integrity

Metallurgical Characterization of the 4.6L
Engine Block Casting
Bulkhead Section
Identification
A
B
C
D
Fatigue, Tensile and Metallographic Test
Samples
E
Bulkhead Sections

Fatigue Environmental Test Chamber
a b c
d
e
f
Figures a) – f) : a) Mounted fatigue test sample inside an environmental test chamber, b) Close up of the mounted fatigue
test sample in high temperature 35 kN capacity grips, c) View of the mounted fatigue test sample inside the environmental
test chamber and temperature controller, d) entire test frame and environmental test chamber, e) Load frame and
environmental test chamber and f) Mounted strain gauge test sample.

Rate of heating for the fatigue test sample and the
environmental test chamber

Staircase Fatigue Testing Methodology
Failure
σ 2
Run out
Mean Stress
(Fully Reversed, R = -1))
σ 1
Δσ
1 2 3
Sample Number
Three fatigue test samples at the beginning of a staircase test. The sequence
would continue until the desired number of tests have been completed.

Effect of Alloy Chemistry
• Freezing Range (FR): Temperature gap between Liquidus (start of phase
growth) and Solidus (complete alloy solidification).
– Si: increasing its concentration shortens FR.
– Cu: increasing its concentration lengthens FR.
W319
Alloy
af s
αDEN
= 43%
Hydrostatically
Stressed liquid
Alloy Si Fe Cu Mn Mg Ni Zn Ti
WA328 9.17 0.372 1.02 0.159 0.310 0.185 0.145 0.076
WB328 8.68 0.833 1.02 0.372 0.300 0.176 0.140 0.074
WA328
Alloy
af s
αDEN
= 30%
Less
Hydrostatically
Stressed liquid
Pores

Example - 4.6L V8 Block
(No chill with λ 2 = 55 mm structure)
120
Fully Reversed Stress (MPa)
(R = -1, Operating Temperature = 120°C)
110
100
90
80
70
60
50
40
30
20
10
0
Passed test (W319 with 70 ppm Sr)
Failed test (W319 with 70 ppm Sr)
Passed test (W319 with Grain refiner)
Failed test (W319 with Grain refiner)
Passed test (WA328)
Failed test (WA328)
0 5 10 15 20 25 30 35
Sample Number

SEM/SE Micrograph of 4.6L V8 Block (WA328) Fatigue
Test Sample #84,933,391
#1
Cycles, 75.8 MPa
Transition line
Pores
1
Shrinkage pores
2
200 μm
#2
3
Interconnected
Shrinkage pore
1 mm
(SEM/SE) micrograph taken from the fatigue test
sample (sample # 8) fracture surface. The stress was at
75.8 MPa & had a life of 4,933,391 cycles. The dashed
boxes are shown at a higher magnification in Figures
6.4.2l, 6.4.2n and 6.4.2p.
200 μm
#3
Cracked Si Particles
100 μm

Maximum Pore Diameter (μm)
1000
900
800
700
600
500
400
300
200
100
0
Relationship Between Porosity & HCF
W319 (Al-5Ti-1B-10Sr)
W319 (Al-5Ti-1B)
af s
αDEN
Maximum Pore Diameter
Mean HCF 4.6L W319 (In-furnace 70 ppm Sr)
Mean HCF 4.6L W319 (In-mould Al-5Ti-1B)
Mean HCF 4.6L WA328
0 20 40 60 80 100
Mean High Cycle Fatigue (MPa)
WA328
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Area Fraction Porosity (%)