Aluminum casting properties depend on alloy, heat treatment and how a test specimen was produced. Armstrong RM publishes typical values for separately cast test bars associated with its precision airset sand-casting alloys. The table organizes selected aluminum entries by alloy and heat treatment, and preserves the source’s strength units, elongation, hardness and qualitative shop ratings. These typical test-bar values are useful for comparison, but they are not guaranteed properties of a finished casting.

Aluminum sand casting alloy properties

Compare alloy and treatment together

Each row combines the alloy designation with its heat-treatment condition. For example, Armstrong lists 356.0-T51 at 25 ksi ultimate tensile strength and 20 ksi minimum yield strength at 2% set, while its 356.0-T6 entry lists 33 ksi and 24 ksi. The T6 entry also reports higher elongation and hardness in the table. Those are reported typical values for the specified test-bar scope, not a universal ranking for every casting made from the alloys.

The source’s “minimum yield strength set @ 2%” wording is retained as published. It should not be silently rewritten as a 0.2% proof-strength value. Strength is in ksi, elongation is a percent, and hardness is on the Rockwell E scale. The A/B/C fields are qualitative Armstrong ratings for pressure tightness and machinability; they are not numeric material properties or acceptance grades.

What the test bars establish

Armstrong states that the values are for separately cast test bars and are typical. A separately cast bar may not experience the same cooling rate, section thickness, feeding, porosity or heat flow as the production component. The mechanical properties of a casting can vary with location and process controls. Consequently, a test-bar table cannot certify the strength or leak-tightness of an individual part.

Heat treatment also needs to match the designation. A T51 and T6 entry is not just a different label on the same property set; the treatment affects the measured values. The exact casting specification, process, section size, heat-treatment record and acceptance testing govern the supplied component. Use the table to understand the source’s reported typical values, then obtain guaranteed design data from the applicable specification and casting supplier.

Use ratings cautiously

The pressure-tightness and machinability columns are letter ratings, with the source defining A as excellent, B as good and C as fair. They summarize the caster’s assessments for the listed alloy/treatment offerings; they do not specify a leak test pressure, machining speed, tool life or production acceptance limit. A pressure-containing design requires its own applicable code, drawing and qualification evidence.

As an example of why designation matters, Armstrong’s A356.0-T6 test-bar row reports 40 ksi ultimate tensile strength, 30 ksi minimum yield at 2% set, 6% elongation and 82.5 Rockwell E. Those values belong to the source’s separately cast test bar and stated heat treatment. Do not apply them to an A356 casting in another condition or use them as a design allowable without checking the controlling material specification.

Limits and material verification

Before using a property, verify the full alloy designation, casting process, heat treatment and applicable specification on the certificate. Confirm whether a drawing calls for a minimum, typical or guaranteed value and which test method controls. For a critical part, obtain representative component data or a supplier-certified value appropriate to the casting’s geometry and quality requirements.

This table does not cover every aluminum casting alloy, temper, section size or manufacturing route. It also does not provide fatigue, fracture toughness, elevated-temperature, corrosion or weldability data. Use a source designed for the engineering decision at hand, and do not substitute typical test-bar values for an approved design allowable or component acceptance requirement.

Source and scope

Data source: Armstrong RM technical information for precision airset sand castings. Armstrong identifies the listed values as typical separately cast test-bar results.