Which material is generally suitable for magnetic particle inspection?

Which material is generally suitable for magnetic particle inspection?

• A. Magnesium alloys
• B. Aluminum alloys
• C. Iron alloys
• D. Zinc alloys

Answer: (C)

Magnetic particle inspection relies on magnetizing a part and looking for leakage fields that form around flaws. Only materials that can be strongly magnetized—ferromagnetic metals—will show this leakage clearly. Iron alloys fit this requirement, so they respond to the magnetic field by concentrating flux at cracks and defects, which draws in the magnetic particles to reveal the flaw. Non-ferromagnetic metals like aluminum, magnesium, and zinc alloys don’t sustain the necessary magnetization under standard MPI conditions, so they don’t produce the detectable flux leakage patterns MPI relies on. Therefore, they’re generally not suitable for magnetic particle inspection. In those cases, other NDT methods are used instead.

Magnetic particle inspection relies on magnetizing a part and looking for leakage fields that form around flaws. Only materials that can be strongly magnetized—ferromagnetic metals—will show this leakage clearly. Iron alloys fit this requirement, so they respond to the magnetic field by concentrating flux at cracks and defects, which draws in the magnetic particles to reveal the flaw.

Non-ferromagnetic metals like aluminum, magnesium, and zinc alloys don’t sustain the necessary magnetization under standard MPI conditions, so they don’t produce the detectable flux leakage patterns MPI relies on. Therefore, they’re generally not suitable for magnetic particle inspection. In those cases, other NDT methods are used instead.