Alloy Composition
High-strength alpha-beta titanium alloys containing six percent aluminum and four percent vanadium represent the standard material for critical aerospace structural components. Commonly designated as Ti-6Al-4V titanium, this alloy exhibits a low electrical conductivity of approximately one percent of the international annealed copper standard. Its low electrical and thermal conductivity requires high-precision eddy current instruments for crack detection and alloy verification.
Electromagnetic Response
Because the alloy is non-magnetic, its electromagnetic response is dictated entirely by its electrical conductivity. The low conductivity requires higher excitation frequencies to generate sufficient eddy currents.
Calibration Protocol
Calibration blocks manufactured from a certified billet of the same alloy are used to set up the inspection equipment. When calibrating for Ti-6Al-4V titanium, the test frequency is set between one and two megahertz to ensure a suitable skin depth for surface defect evaluation. This high frequency maximizes the phase angle separation between lift-off and defects.
Inspection Challenges
The material has a very high acoustic attenuation, which makes ultrasonic testing difficult and increases the reliance on electromagnetic surface inspection. Inspection operators must maintain a constant probe angle to prevent false indications from lift-off variation. The permissible surface scratch depth for reference standards is kept below fifty micrometers to ensure high measurement precision.
