The effect of phase distribution of constituent-fiber structure on the deformation heterogeneity of TRIP-assisted lean duplex stainless steel

Abstract

The cold-rolled TRIP-assisted lean duplex stainless steel (TLDX) showed the directional distribution of constituent-fiber structure. The effect of phase distribution of constituent-fiber structure on the deformation heterogeneity during tensile tests and deep drawing of cylindrical cup was investigated through crystal plasticity finite element model (CPFEM) involved in the martensitic transformation. The results showed that the strain for the plastic instability was lower in the transverse direction (TD)-loaded case (true strain εT ∼0.408) compared with the rolling direction (RD)-loaded case (εT ∼0.485). Also, the strain localization bands formed at a lower strain (engineering strain εE ∼40%) in the TD-loaded case than that in the RD-loaded case (εE ∼55%). At the same strain, the volume fraction of transformed martensite of the TD-loaded case was relatively less than that of the RD-loaded case. For the transformed martensite, it only accommodated a low proportion (<5%) of global strain in the two cases. The proportion of partitioned strain into austenite (Pεγ) in the RD-loaded case was always higher than that in the TD-loaded case, while the partitioned strain into ferrite (Pεα) showed a converse law, which indicated that the deformation heterogeneity in the TD-loaded case is more pronounced. Similarly, the high risk of cracking of deep-drawn cylindrical cups with different sizes also always formed at the specific zones corresponding to the TD-loaded case.