The document discusses materials used for engine blocks. It notes that engine blocks require high strength, modulus of elasticity, abrasion and corrosion resistance, as well as low density, thermal expansion and conductivity. Early blocks were made of cast iron due to strength and cost, but aluminum alloys increased in use during the 1960s-70s as they improve fuel efficiency and performance. Magnesium and compacted graphite cast iron are also used. Common aluminum alloys for blocks include 319 and A356, while gray cast iron provides damping and machinability but is weaker.

1. Engine blocks Materials
K.G.Maheswaran

2. Required Material Properties
• High strength
Diesel engines-High strength is a concern (As CR >17)
• High Modulus of elasticity
• High Abrasion resistance
• High Corrosion resistance
– Should also have a
• Low density,
• Low thermal expansion (to resist expanding under high
operating temperatures)
• Low Thermal conductivity (to prevent failure under high
temperatures)

3. • Good machinability and castability
• Good vibration damping (to absorb the shuddering of
the moving parts)
• Required mechanical properties for a
typical aluminum engine block
• Ultimate tensile strength of 245 Mpa
• Yield stress of 215 Mpa
• Fatigue strength of 60 MPa

4. Engine blocks Materials
• Constitutes 20-25% of the total weight of an engine
• Cast iron alloys-Early engine blocks were
manufactured from primarily due to its high
strength and low cost
• Aluminum alloys-Used sparingly in the 1930’s
• Increased during the 1960’s and 1970’s
• Aluminum alloys increase fuel efficiency and
performance.

5. • Magnesium alloy-AMC-SC1-weighs less than
both cast iron and aluminum alloys
• Diesel engine blocks-compacted graphite cast
iron (CGI)-alternative to gray cast iron

6. Gray cast iron alloys
• Gray cast iron alloys typically contains
• 2.5-4 wt.% Carbon
• 1-3 wt.% Silicon• 1-3 wt.% Silicon
• 0.2-1.0 wt.% Manganese
• 0.02-0.25 wt.% Sulfur
• 0.02-1.0 wt.% Phosphorus

7. Gray cast iron alloys -Properties
• Excellent damping capacity,
• Good wear and temperature resistance,
• Easily machinable, and is inexpensive to
produceproduce
• But are relatively weak and are prone to fracture
and deformation

8. Compacted Graphite Cast Iron
• Higher tensile strength and elastic modulus than
gray cast iron
• Good damping capacity and thermal conductivity,
• Difficulty to machine
• 150,000 Ford/Peugeot’s diesel

9. Aluminum Alloys
• ADV:
• Improved performance-to-weight ratio and
increased fuel efficiency
• DISADV:• DISADV:
• More expensive to manufacture THAN Cast iron
alloys
• NOW Cost IS Decreased

10. Aluminum Alloys Composition
Aluminum alloy 319
• 85.8-91.5 wt.% Aluminum
• 5.5-6.5 wt.% Silicon,
• 3-4 wt.% Copper
• Maximum 0.35 wt.% Nickel• Maximum 0.35 wt.% Nickel
• Maximum 0.25 wt.% Titanium
• Maximum 0.5 wt.% Manganese,
• Maximum 1% Iron,
• Maximum 0.1 wt.% Magnesium
• Maximum 1 wt.% Zinc

11. Aluminum Alloys Properties
• Good casting characteristics
• Good corrosion resistance
• Good Thermal conductivity

12. Aluminum alloy A356
• 91.1-93.3 wt.% Aluminum
• 6.5-7.5 wt.% Silicon
• 0.25-0.45 wt.% Magnesium• 0.25-0.45 wt.% Magnesium
• maxima of 0.2 wt.% Copper
• 0.2 wt.% Titanium
• 0.2 wt.% Iron
• 0.1 wt.% Zinc

13. Magnesium Alloys
Used as
• Valve covers
• Cylinder head covers
• Intake manifolds• Intake manifolds
• Rocker arm covers
• Air intake adaptors
• Induction systems
• Accessory drive brackets

14. Sand-cast AMC-SC1 magnesium alloy
• This grade of magnesium alloy contains two rare earth
elements,lanthanum and cerium, and was heat-treated
with T6.
Other properties of the magnesium alloy
• Good thermal conductivity,
• Excellent machining and casting qualities,
• Excellent damping characteristics

15. Auto bodies:
Some, such as Audi and Jaguar are now using aluminium
(5xxx series alloys).
Steel is still the main metal with a mixture of HSLA steelSteel is still the main metal with a mixture of HSLA steel
(high stength, low alloy), TRIP (transformation induced
plasticity) and rephosophorised types - these are almost
exclusively galvanised or galvanealed.
speeds requires a low reciprocating mass

16. • Crank shaft (car and bike)
These tend to be forged from low alloy chromium-
molybdenum steel (sometimes chromium-moly-
vanadium).
• Some of these will be nitrided to improve fatigue
resistance (depends on manufacturer).

17. • Piston
This is a tricky one. There has been a move
towards piston crowns being made of hyper-
eutectic aluminium-silicon alloys for petrol
(gasoline) engines. While some diesels have
aluminium crowns (with oil injection underneath
to keep the crown cool), some are still based on
low alloy steel.
• Bike engines are almost exclusively aluminium as
the high engine

18. Con-rods
With the exception of the ultra-trick titanium rods on some
very highly stressed engines (bike racing mainly), these are
also low alloy steels of the same type as the crank.
Cylinder blocks are nearly all aluminium now.
BMW have developed a magnesium block with a seperateBMW have developed a magnesium block with a seperate
cast-in aluminium cylinder casting.
Ford, Toyota, Peugeot/Citreon, Land-Rover all use cast iron
cylinder liners in an aluminium block (some pushed in,
some cast in).
BMW and VAG use aluminium liners in (mainly) aluminium
blocks