Solid Solution And Aging Treatment On 00cr25ni35alti Microstructure And Properties Of The Study

00Cr25Ni35AlTi is an austenitic Fe-Ni-Cr alloy that is developed by our country,and it is mainly applied to stream generator(SG)heat transfer tube of nuclear power unit due to its excellent corrosion-resistant properties in high temperature and high pressure water.In this paper,the effects of solution and aging treatment on microstructure,mechanical properties,pitting corrosion and intergranular attack(IGA)resistant properties of 00Cr25Ni35AlTi are studied by optical microscope,scanning electronic microscope(SEM), transmission electron microscope(TEM),X-ray diffraction(XRD)and physics-chemistry phase analysis.The main conclusions are as follows:(1)With the solution temperature and time increasing,the grain size grows,and the plasticity increases,while the strength decreases.The relationship between grain size and strength meets the Hall-Petch relation formula.(2)The solution temperature increases at 900℃～1100℃and improves the pitting resistant properties,while it is unfavorable for IGA resistant properties after aging treatment.(3)The alloy doesn't reach ideal recrystallization and lots of Cr-rich carbide precipitates along the original grain boundaries below 980℃solution.Grain size grows quickly above 1050℃.The optimum heat treatment process is 1000℃for fine and homogeneous structure, and the grain size is above 9 grade.(4)The main precipitate phases are Cr-rich M₂₃C₆ during 550～950℃aging treatment after solution at 1050℃for half an hour.The content and size of precipitation M₂₃C₆ increase with the aging temperature from 550℃to 850℃.At the same time the morphology also turns from thin rods into flake and acute triangular form in the end.At 950℃,the content of M₂₃C₆ is partly dissolved.Most of the M₂₃C₆ distributes along grain boundary and at the end of twin boundary,but there is no evidence of M₂₃C₆ ill the coherency twin boundary and matrix.(5)Pitting resistant and IGA resistant properties are lower after aging treatment.Corrosion resistant properties reach the worst point at 700℃×2h because of the minimum chromium concentration nearby the grain boundary.The research of this article has provided reliable theory and test basis for manufacture and application of SG tube.