EFFECT OF INCLUSION ORIENTATION UPON ACOUSTIC-EMISSION MICROSTRUCTURAL RELATIONSHIPS IN FERRITIC STEELS

A comparison of the acoustic emission, mechanical properties and fract ure behaviour of three model low-alloy steels containing manganese sul phide inclusions of varying orientation has been made as a function of tempering conditions. The majority of the inclusions existed in ellip tical clusters whose major axis was aligned with the rolling direction and whose plane lay on the rolling plane. Both the yield region acous tic emission activity and ductility in the through-thickness (short tr ansverse) sample orientation were reduced compared with the longitudin al, and to a lesser extent, transverse orientation samples. These effe cts are shown to be a consequence of inter-inclusion cluster shear loc alization in material of high yield stress and low work-hardening capa city. Because of the wide range of yield strengths and work-hardening capacities used in this study, the results extend our insight of the i nteractions between inclusion distribution, stress state and work-hard ening capacity during ductile fracture of this class of materials.