Acoustic emission during tensile deformation of annealed and cold-worked AISI type 304 austenitic stainless steel

Abstract

The influence of prior cold work on the acoustic emission (AE) generated during subsequent plastic deformation of AISI type 304 stainless steel has been studied. AE parameters such as root mean square voltage, ringdown counts, etc., have been used to analyse the data. AE generated during tensile deformation is affected by prior cold work. The increase in acoustic activity at low strain levels in a less cold-worked (10%) specimen compared to a solution-annealed specimen was attributed to the easy formation of α'-martensite assisted by prior cold work. The decreased acoustic activity for higher cold-worked (20%, 40%, and 50%) specimens at low strain levels was attributed to reduced glide distance for moving dislocations and reduced amount of α'-martensite formation. The AE activity was found to be maximum during higher strain values in the solution-annealed specimen compared to the cold-worked specimens. This was attributed to relatively larger amount of α'-martensite formation in the solution-annealed specimen. Eddy current testing, X-ray diffraction, remanent magnetization measurement and magnetic etching techniques have been used to corroborate the AE results. Among these, remanent magnetization results were found to have good correlation with the AE results.