Effect Of C Content And Cold Deformation On Microstructure And Properties Of OCr25Ni35AlTi Alloy

0Cr25Ni35AlTi alloy is a kind of self-dependent Fe-Ni-Cr alloy suitable for the harsh environment. Due to its excellent intergranular corrosion resistance and mechanical properties, it is used for PWR heat transfer tube device of steam generator. Mechanical properties and corrosion resistance of 0Cr25Ni35AlTi alloy are closely related with its composition, especially the carbon content of the alloy. Therefore, systematical study on the influence of carbon content on organization and properties of the alloy was of significant theoretical sense and practical application value for the optimization of composition and processing technology of 0Cr25Ni35AlTi alloy.The microstructure, mechanical properties, precipitates and deformation characteristic were observed and analyzed by employing the methods of physicochemical phase analysis, scanning electron microscopy and transmission electron microscopy. Moreover, through weight loss and electrochemical method, corrosion resistance of 0Cr25Ni35AlTi alloy was tested.The research results showed that with increase of carbon content, the average grain size decreased, the number of M23C6 precipitation increased, mechanical properties was improved, and however, intergranular corrosion resistance was deteriorated obviously. It can be concluded that carbon content of the alloy should be controlled at about 0.025%, making it has a good resistance to intergranular corrosion and still strength higher than 300MPa to meet the mechanical properties index. Cold deformation has important influence on mechanical and corrosion properties of 0Cr25Ni35AlTi alloy, with increasing of the deformation, the number of bending deformation and twins increased in deformation zone, which resulted in the increase of strength and hardness, and the reduction in both the plasticity and work hardening capacity. Meanwhile, pitting corrosion resistance was weaked. As the carbon content increased, the amount of precipitation increased, and the precipitates grew up and gathered, leading to the reduction in corrosion resistance. After aging at 650℃ for 2h, corrosion resistance was deteriorated to the largest degree because of the formation of chromium-depleted zones nearby the grain boundary. On the basis of hot compression tests, the hot deformation constitutive relationship which can relate flow stress to deformation temperature and strain rate was obtained for hot deformation of this alloy. It can be found from the results of observation of recrystallization behavior of the specimens deformed under different deformation conditions that increasing deformation temperature or reducing strain rate is conducive to dynamic recrystallization during hot deformation. The carbon content has obvious influence on dynamic recrystallization process, as the carbon content increases, dynamic recrystallization process become sluggish. It was deduced that the hot deformation activation energy and deformation resistance increased with carbon content.