Using strain rate sensitivity measurements to determine phase relations in A430 stainless steel

Precision strain rate sensitivity measurements have been used to determine the solid solution component of interstitials in ferritic stainless steel. The measurements are based on activation volume of dislocation-solute interaction. Under an instantaneous strain rate change, a load drop occurs which is inversely proportional to the activation volume. By correlating the measured response with heat treatments a pseudo-binary Nb(C,N) solvus was determined. Such a phase diagram for a specific stainless steel alloy is useful for delineating hot-working conditions. The technique was also able to detect the presence of fine Guinier-Preston zone type of precipitates that formed during quenching and were aligned with the {001} planes of the matrix.