Path Correlation And Non-Masing Characteristic Analysis Of DSA Effect Of 316L Stainless Steel

Due to the rapid development of nuclear power,petrochemical industry and mechanization,the large scale,complexity and high parameterization of the production scale greatly increase the probability of fatigue failure of zero-component.Therefore,the research on multi-axis fatigue of materials is of great engineering significance.316 L stainless steel is widely used in chemical industry,nuclear power and other fields due to its excellent corrosion resistance,high tensile strength at high temperature and good comprehensive mechanical properties.In practical use,the vessel made of this material is usually used in the temperature range of 573?673K,which happens to be located in the DSA temperature range of 316 L stainless steel.Therefore,the study on DSA effect has important reference significance for the engineering application of 316 L stainless steel.In this paper,the path correlation of DSA effect of 316 L stainless steel and the nonMasing characteristics under different conditions are studied,and the main conclusions are as follows:First of all,based on the low cycle fatigue experiment of 316 L stainless steel 873 K circular path with different strain ranges,the correlation between cycle number,strain range and loading state of DSA was analyzed.The results show that DSA phenomenon is obvious at the beginning of the cycle,and then gradually weakens.A large number of Snoek solute atom air masses are generated before the failure under large strain amplitude,which makes DSA phenomenon again significant at this stage.From the correlation analysis of strain range,it can be seen that the stress drop and sawtooth density increase with the increase of strain range,and the dislocation proliferation leads to the increase of sawtooth number under large strain range.The thermodynamic analysis shows that the diffusivity of the vacancy is restrained by hydrostatic pressure and the sawtooth yield is more obvious during the compression phase.The results of scanning electron microscope show that the failure of materials in the two strain range is the result of fatigue,dynamic strain aging and oxidation.Secondly,based on the low cycle fatigue experiments of 316 L stainless steel under different strain ranges of 293 K and 873 K,the amplitude correlation and temperature correlation of material cycling characteristics were discussed,and the non-Masing characteristics under different conditions were compared.The experimental results show that cyclic hardening occurs at the beginning of each cycle,then cyclic softening,saturation and failure occur.The non-masing phenomenon at 293 K was more significant than that at873 K.The non-Masing properties at both temperatures are enhanced with the increase of strain range.Finally,the fatigue life was predicted by using the energy method,and the predicted results were all located in the twice dispersion zone.However,considering the non-masing characteristics,more accurate prediction results were obtained than the Masing characteristics.Under the large strain range of 873 K,the significant dynamic strain aging results lead to the prediction results of non-Masing and Masing characteristics are not different from each other.