Gas porosity appears as small, round, or elongated dark spots on a radiograph. It is caused by gas bubbles becoming trapped in the metal as it solidifies. ASTM E155 provides reference images showing different densities of gas porosity, allowing inspectors to determine if the distribution is within acceptable limits for the specific grade of casting.

Aluminum and magnesium alloys are lightweight materials extensively used in aerospace, automotive, and defense industries. However, their low density and unique solidification behaviors make them prone to specific types of porosity and shrinkage. Standard steel radiographs (like ASTM E446 for steel) are not applicable because the X-ray absorption characteristics of aluminum and magnesium are vastly different. Hence, ASTM E155 is the dedicated standard for these critical alloys.

Your casting shows a dark, feathery pattern. Based on training, you suspect it is shrinkage – dendritic .

In the world of nondestructive testing (NDT) and manufacturing quality assurance, precision is paramount. When dealing with metal castings—particularly those made from aluminum and magnesium—internal discontinuities can be the difference between a reliable component and a catastrophic failure. For engineers, radiographers, and quality control professionals, one document has stood as the gold standard for decades: .

ASTM E155 does not replace the need for IQIs (e.g., penetrameters). The reference radiographs assume a certain level of radiographic sensitivity. If your technique does not meet that sensitivity, the comparison is invalid.

The standard addresses a wide array of potential discontinuities that can occur during the casting process. Without ASTM E155, describing a defect would be subjective. One inspector might call a flaw "minor," while another might reject the part entirely. ASTM E155 removes this subjectivity by providing a visual dictionary of defects.

The standard arranges discontinuities in ascending order of severity. For example:

A: Follow this format: ASTM E155-20, Standard Reference Radiographs for Inspection of Aluminum and Magnesium Castings, ASTM International, West Conshohocken, PA, 2020, DOI: 10.1520/E0155-20.