Nonlinear ultrasonic assessment of precipitation hardening in ASTM A710 steel

We investigated several specimens of ASTM A710 steel containing copper-rich precipitates with variations in the final aging treatment. X-ray diffracti on line-broadening and small-angle neutron-scattering experiments revealed the existence of the precipitates and associated coherency strain. We deter mined the nonlinear ultrasonic parameter beta for each specimen by harmonic -generation experiments and measured the ultrasonic longitudinal velocity u psilon(L) and attenuation alpha(L). Although upsilon(L) and or, showed no c onsistent trends, beta increased with increasing strain. This correlation i s compared to a microstructural model for harmonic generation that includes a contribution from precipitate-pinned dislocations.