Study On Hot Deformation Behavior And Mechanism Of Economical Duplex Stainless Steel2101

Economical duplex stainless steel (EDSS) is a new kind of duplex stainless steelwith the approximately equal volume fraction of austenite and ferrite, which ownshigher strength, better corrosion resistance, low Ni and low cost. Nickel acts as anaustenite stabilizer in the DSSs, it can be partial or full replacement with manganese andnitrogen as same effect as nickel. High manganese element ensures that the balance ofaustenite and ferrite. However, different thermal expansion coefficients and deformationbehavior of constituent phase, austenite or ferrite in the duplex structure, can easilycause the defects of microstructure and property during hot deformation such as edgecracking and surface cracking, which will seriously affect the quality of products andsubsequent processing. Therefore, the hot deformation behavior and soften mechanismof EDSS were studied in this paper, attempts to establish the theoretical basis foroptimum hot working condition, which is necessary to improve the properties ofmaterials and production rate.The hot compression tests (temperature range of1000–1150°C and strain raterange of0.01–10s-1) of EDSS2101were carried out on Gleeble–1500Dthermo-simulation machine. The hot deformation behavior, soften mechanism andmicrostructure evolution were studied. The constitutive equation under the experimentalconditions was established. Based on the Dynamic Materials Model and the criterions ofPrasad’s and Murty’s were used for the estimation of flow instabilities, the processingmap was constructed in the experimental conditions. The results show that the flowstress increases with the increase in strain rate and the decreases in temperature.Moreover, the like steady state can be observed within a true strain about0.1at temperature of1000°C and high strain rate of10s-1. Influence of deformationconditions (temperature, strain rate and strain) on microstructure evolution ofeconomical duplex stainless steel2101is significant, and the deformation behavior andsoften mechanism is that ferrite take occurrence of dynamic re-crystallization, γ/δ phasetransformation and austenite take occurrence of dynamic recovery. The Arrhenius-typeconstitutive model of peak stress and considering the compensation of strain were usedto predict the flow stress curves under different deformation conditions. Compared withexperimental data, the constitutive model can be used to predict flo w stress preciselyexcept at temperature of1273K and strain rate of10s-1. The high correlation coefficient(R=0.996) and the low average absolute relative error (4.2%) for the flow stressobtained from the established model can be used to numerically simulate the hotdeformation of economical duplex stainless steel2101. According to the result of twodifferent criterions of processing map and microstructure under different deformationconditions, an optimum hot working domain was established: strain rate of0.1–0.3s-1,temperature range of1080–1130°C, in which the dynamic re-crystallization is adequateand peak power dissipation efficiency is more than45%.