Damage development during the strain induced phase transformation of austenitic stainless steels at low temperatures

The strain-induced martensitic transformation greatly affects the plastic behavior of the metastable austenitic stainless steels. The martensitic transformation continuously changes the initially homogeneous material into a strongly heterogeneous bi-phase one. In addition to the hardening behavior, this phenomenon would influence the damage growth and load-carrying capacity of the material during the plastic deformation. In this study, plastic behavior of the material AISI 304 including the hardening and damage growth, has been examined at low temperature; where a high rate of martensitic transformation affects the microstructure strongly. Experimental analysis and microscopic observations have been performed for evaluating the martensite content and damage growth. In addition, based on the continuum damage mechanics, a simplified damage evolution model has been proposed to capture the effect of phase transformation on the damage growth rate explicitly. The results show that the damage initiates with a considerable rate in early stages of transformation, however at higher levels of transformation, damage growth rate decreases until a sudden fracture. The presented model properly predicts the observed damage behavior.