Phase Field Simulation And Experimental Study On The Precipitation Process Of Fe-Cu-Mn Alloy Under Temperature,Mn Content And External Strain Regulation

When Cu-containing steel undergoes irradiation or aging treatment,a nanoscale Cu-rich phase precipitation phenomenon occurs,which produces precipitation strengthening effect to enhance the mechanical properties of the steel,such as yield strength,tensile strength,and hardness.However,in the application of nuclear reactor pressure vessel(RPV),the irradiation of radioactive nuclides will cause the Cu,Ni,Mn,and other elements enriched in the steel to form irradiation induced phase and accelerate the evolution of the phase and the occurrence of intergranular embrittlement,which limits the service life and safety performance of the nuclear reactor.In order to prepare high strength alloy steel or avoid the occurrence of thermal brittleness phenomenon during irradiation service,it is particularly critical to control the Curich phase precipitation behavior to improve the comprehensive performance of the steel.In solid-state phase transformations,temperature,applied stress,and different alloy compositions have significant effects on the precipitation transformation path and microstructure morphology.Therefore,it is of great significance to explore the regulation rules of temperature,applied stress,and alloy composition on the transformational microstructure.In this study,a Fe-Cu-Mn ternary phase field model was established to investigate the transformation mechanism of the Fe-CuMn alloy during aging under the influence of temperature,applied stress,and Mn content,and to elucidate the regulation rules of temperature,applied stress,and Mn content on the transformational microstructure and growth kinetics.The effect of Mn content on the precipitation of Cu-rich phase in the Fe-Cu-Mn alloy was also experimentally studied.By using phase field simulation to explore the effect of temperature on the precipitation of Cu-rich phase in Fe-Cu-Mn alloy,the simulation results showed that temperature could affect the incubation period of the Cu-rich precipitation phase.The incubation period of the Cu-rich precipitation phase was longer at a higher temperature.The reason was that as the temperature increased,the driving force gradually decreased,and the critical nucleation size needed to overcome the nucleation barrier was reduced,resulting in a decrease in the number of particles.By using phase field simulation to explore the effect of applied stress on the precipitation of Cu-rich phase in Fe-Cu-Mn alloy,after adding external stress,the particles showed a clear orientation growth pattern,and the direction of particle growth was perpendicular to the direction of applied strain.As the external stress increased,the trend of Cu-rich precipitation phase growing towards the direction perpendicular to the external stress became more apparent.By using a combined approach of phase field simulation and experiment to explore the effect of Mn content on the precipitation of Cu-rich phase in Fe-Cu-Mn alloy,the increase of Mn content decreased the nucleation energy of the precipitation phase,thus accelerating the process of precipitation strengthening.Atomic structure analysis showed that Mn primarily occupied the Cu sub-lattice and preferred the Cu nanocrystals in terms of energy,which not only increased the driving force of the Cu nanocrystals but also lowered the nucleation strain energy of the Cu nanocrystals.