Austenitic Fe-30Mn-6Si and Fe-30Mn-3Si-3Al steels are known to show shape memory effect related to γ to ε martensitic transformation and TWIP (Twinning Induced Plasticity) effect, respectively. Recently, the present authors investigated the shape memory effect and ductility of Fe-30Mn-(6-x)Si-xAl (x=0 to 3) alloys. As a result, it was found that the shape memory effect was observed in the samples with x=0 and 1, but disappeared when x exceeds 2. The ductility almost linearly increased with increasing the amount of Al. In the present article, the influence of Al concentration on the deformation behavior and fracture mode of these alloys is discussed based on micro-structural and Fractographic observations. The XRD measurements and TEM observations revealed that the deformation behavior gradually changes from the stress-induced martensitic transformation to the deformation twinning with increasing Al. The SEM Fractography on the specimens ruptured at room temperature demonstrated that the dominant fracture mode also gradually alters, being affected by the variation of the deformation behavior. The specimen with x=0 showed step-like ridges on the fracture surface due to a quasi-cleavage transgranular fracture along fine ε plates, which is ascribed to the stress-concentration at the intersection between primary and secondary ε plates. With increasing Al, however, the probability of the step-like ridges decreases, while coarse deep dimples become prominent. The fracture surface of the specimen with x=3 was fully covered by dimples indicating a ductile fracture mode