MICROMECHANISMS OF DEFORMATION OF AN AUSTENOFERRITIC DUPLEX STAINLESS-STEEL

Slip transmission through austenite-ferri-e coherent interfaces is stu died using transmission electron microscopy (TEM) and in-situ TEM at r oom temperature and high temperatures, on as-received and on aged spec imens. It is shown that austenite deforms first, and that slip transmi ssion from austenite to ferrite is effective only for the slip systems which are shared by the two phases. Deformation in ferrite is fairly homogeneous in the as-received state, but becomes quite localized in t he aged material. In this case, sluggish anti jerky glide of short edg e dislocations coming from the interface generates long screw dislocat ions, which experience a strong Peierls frictional stress. A simple mo del is proposed for strain localization, which qualitatively accounts for slip band separation and interfacial step heights as a function of temperature, in terms of the amount of hardening due to spinodal unmi xing of aged ferrite and of the variations with temperature in both th e yield stress and the work-hardening rate of ferrite.