Most cast aluminum engine blocks are typically made from one of three specific alloys: 319, A356, or A357.
Aluminum alloys have become increasingly popular for engine blocks due to their lighter weight compared to cast iron, which improves fuel efficiency and overall vehicle performance. The specific alloys chosen offer a balance of castability, strength, durability, and heat resistance required for the demanding environment inside an engine.
Common Aluminum Alloys for Engine Blocks
While other alloys might be used in specific applications, the reference highlights three prevalent types for cast blocks:
- 319 Alloy: A widely used general-purpose casting alloy. It's known for its excellent castability and good mechanical properties.
- A356 Alloy: This is a heat-treatable casting alloy primarily composed of aluminum and silicon, with added magnesium. It offers very good castability and can achieve high strength and ductility after heat treatment.
- A357 Alloy: Similar to A356 but with a higher magnesium content and sometimes beryllium or strontium additions. It can achieve even higher strength properties after heat treatment, making it suitable for high-performance applications.
Composition of 319 Aluminum Alloy
The reference provides a detailed breakdown of the typical composition range for the 319 alloy, illustrating why it's a suitable choice for casting complex engine block shapes.
| Element | Percentage Range |
|---|---|
| Aluminum | 85.8% to 91.5% |
| Silicon | 5.5% to 6.5% |
| Copper | 3% to 4% |
| Iron | 1% |
| Zinc | 1% |
| Manganese | 0.5% |
| Nickel | 0.35% |
| Titanium | 0.25% |
| Magnesium | 0.1% |
This specific mix of elements contributes to the alloy's properties, such as its ability to fill intricate molds during casting and its strength once solidified. Silicon improves fluidity for casting, copper adds strength, and other elements refine the structure or add specific properties.
The choice among these alloys (319, A356, or A357) often depends on the specific design requirements, performance goals, and cost considerations for the engine. High-performance engines might opt for the A356 or A357 due to their superior strength capabilities after heat treatment.
