| Due to the difference of lattice constants between various components,high entropy alloys are not coherent,so complex structural and morphological changes will occur in the process of phase transformation.As a result,this kind of multicomponent alloys usually have excellent oxidation resistance,high-temperature mechanical properties,heat resistance and other characteristics,so that they are widely used in important parts and harsh working environment in many fields such as aerospace,military industry and so on.Changing the microstructure and morphology of the alloy through the composition design of the alloy is one of the main means to improve the performance of the alloy.However,in order to achieve this goal,we must first understand the evolution law of coherent microstructure in various alloy systems,so as to carry out more targeted composition design of the alloy.The traditional experimental methods are not only time-consuming,laborious and expensive,but also can not capture the micro evolution of the structure in real time.The simulation method can greatly shorten the experimental cycle and save money.It can also observe and predict the evolution of the microstructure and the morphological changes of the second phase precipitates.In this paper,CALPHAD and continuous phase field model are mainly used to study the microstructure and Phase Transformation Microstructure Evolution of Fe-Mn-Cr-Ni-Al high entropy alloy,simulate and calculate,and study its phase transformation law from the microscopic point of view.The main results are as follows:The results show that the larger the gradient energy coefficient is,the smaller the volume fraction and number of particles are,and the larger the average particle size is;The energy barrier has little effect on the number of particles and is inversely proportional to the average particle size;Lattice distortion,anisotropy of elastic modulus and applied strain have great effects on the morphology of precipitated phase.Secondly,using the continuous phase field model of Fe-Mn-Cr-Ni-Al high entropy alloy,when the temperature is less than 400 ?,there is only BCC phase in the matrix.When t = 600 ?and the Al content is 0.1,the transformation from FCC to BCC will occur,and the higher the temperature is,the higher the Al content required for phase structure transformation is;When the temperature is maintained at 1000 ?,the higher the Cr content,the lower the Al content required for phase structure transformation,indicating that Cr will promote phase structure transformation.The higher the Al content,the roundness,volume fraction and particle size will increase;Cr content can promote the precipitation of precipitates,but has little effect on the size and quantity of precipitates.Under the action of elastic anisotropy,the precipitate phase will grow along the softening direction of the matrix,and there is a significant correlation with the appearance of the precipitate phase.Through the above conclusions,it is found that the phase field method,as a practical tool for micro evolution,simulates the micro evolution dynamic process of precipitated phase under different composition and temperature,and uses CALPHAD method to prove the potential of optimizing alloy chemical composition to improve the structural stability of BCC / B2 and predict the appearance of precipitated phase. |
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