356
By far the most common alloy used in prototyping die-castings is Aluminum Association 356. It offers good cast ability, pressure tightness, and surface appearance. When combined with a T6 (solution heat-treated and artificially aged) it provides the following typical mechanical properties as minimums.
Tensile Strength – 35,000 to 40,000 PSI
Yield Strength – 25,000 to 30,000 PSI
Elongation 3 – 6%
A caution regarding 356 Aluminum is that its heat dissipation characteristics are approximately150% those of die cast 380 (in other words it offers greater heat dissipation than the die cast 380). This can deem it inappropriate for some heat sensitive prototypes. Its heat transfer does match die cast 443 Aluminum.
319
When used as a prototyping alloy 319 closely mimics heat transfer characteristics of die cast 380. It offers the following typical mechanical properties as minimums when produced with a T6.
Tensile Strength – 30,000 to 36,000 PSI
Yield Strength – 21,000 to 24,000 PSI
Elongation 2.5%
Although its copper content matches 380, its elevated levels of other trace elements produce a part that does not paint, chem. film, or coat as well as some other alloys. This along with some susceptibility to corrosion has relegated it mainly to prototyping of heat sinks and cylinder heads.
380
In circumstances where strength is not a particular issue for protyping, 380 Aluminum can be used. Examples of this could be switch plates, electronics enclosures, bezels, and other non-structural components.
Others
Other alloys can at times be used to test for a narrower range of characteristics. Examples of this might be 355 Aluminum for minimized elongation of some trans axle components. 360 and or 390 may be suited for clutch or other “wear sensitive” components. Depending upon testing required sometimes the same casting design would be produced in multiple alloys.
Zinc
#12 gravity cast zinc mimics mechanical properties of die cast 3, 5, or 8 zinc. Die cast #12 zinc can be prototyped in #27 zinc.