The evolution of micro- and macrostresses in a duplexstainless steel during loading has been investigated in situ byX-ray diffraction. A 1.5 mm cold-rolled sheet or alloy SAF 2304solution treated at 1050?C was studied. Owing to differences inthe coefficient of thermal expansion between the two phases,compressive residual microstresses were found in the ferriticphase and balancing tensile microstresses in the austenitic phase.The initial microstresses were almost two times higher in thetransverse direction compared to the rolling direction. Duringloading the microstresses increase in the macroscopic elasticregime but start to decrease slightly with increasing load in themacroscopic plastic regime. For instance, the microstressesalong the rolling direction in the austenite increase from 60 MPa.at zero applied load, to 110 MPa. at an applied load of 530 MPa.At the applied load of 620 MPa a decrease of the microstress to90 MPa was observed. During unloading from the plastic regime themicrostresses increase by approximately 35 MPa in the directionof applied load but remain constant in the other directions. Theinitial stress state influences the stress evolution and evenafter 2.5% plastic strain the main contribution to themicrostresses originates from the initial thermal stresses.Finite element simulations show stress variations within onephase and a strong influence of both the elastic and plasticanisotropy of the individual phases on the simulated stress state.
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