Finding new strength in aluminum: fuel efficiency-driven weight reduction issues in heavy-duty transportation have made high-strength aluminum alloys, such as A206, desirable alternatives to A356.

The constant drive to reduce part weight for automotive applications makes aluminum alloys attractive candidates for producing structural components because they are lighter than ferrous metals while featuring the necessary properties to meet the structural requirements. The highly castable A356 alloy has emerged as the most popular aluminum alloy for automotive chassis and suspension components, but its limitations in yield strength, fracture toughness and fatigue strength has kept high-strength- low alloy steel fabrications the norm in heavy-duty transportation applications.

Because the demand for better fuel efficiency in heavy-duty vehicles increasingly calls for lighter parts, the demand for castings made of high-strength aluminum alloys, such as A206, is increasing.

Although 20% more expensive than A356. A206 has superior fracture toughness and fatigue properties. But A206, which typically consists of 4.2-5% copper. is a long feeding range alloy prone to shrinkage defects with a reputation for hot cracking (though a modified version with a lower propensity for hot cracking has been developed). To work through these potential defects, casting optimization technology be comes important.

Casting optimization technology is a powerful tool that can provide the upfront engineering necessary to produce high quality A206 castings.

This article illustrates the efforts expended on the substitution of a large structural steel welded fabrication with an A206 alloy casting for a heavy specialty truck.

Material Selection

Field loading conditions for a large structural casting (LSC) used in the suspension system of a heavy-duty truck warranted a material that could withstand severe loading and fatigue conditions (Fig. 1). Only two …