Controlling microstructure in nickel 200, titanium grade 2, and titanium grade 5 for the calibration of ultrasonic microstructure characterization

Ultrasonic testing is a promising technique by which to nondestructively determine the subsurface material microstructure characteristics of metallic components. Development of this technique requires reference specimens of known microstructure by which to calibrate the ultrasonic signal response. Such reference specimens were produced in Nickel 200 (commercial-purity Ni or Ni 200), Titanium Grade 2 (commercial-purity Ti or TiGr2) and Titanium Grade 5 (Ti-6Al-4V or TiGr5) materials in the laboratory. The microstructures produced and methods of their production are presented and discussed. Particular attention is given to techniques appropriate in the general research laboratory environment. Recrystallized grain size is controlled across a wide range in the Ni 200, TiGr2, and TiGr5 materials by annealing after cold rolling. Heat treatments and hot compression further produced fully lamellar, duplex, and equiaxed (globular) microstructure forms in the TiGr5 material. The theory of ultrasonic signals interacting with grain boundaries and grain/phase interfaces will be discussed in light of the microstructures produced within these specimens