The microstructures and their kinetics of normal grain growth are simulated using different Monte Carlo （MC） algorithms. Compared with the relative figures and the theoretical normal grain growth exponents of n =0.5...The microstructures and their kinetics of normal grain growth are simulated using different Monte Carlo （MC） algorithms. Compared with the relative figures and the theoretical normal grain growth exponents of n =0.5, the effects of some factors of MC algorithm, i.e. the lattice types, the methods of selecting lattice sites, and the neighbors selection for energy calculations, on the simulation results of grain growth are studied. Two methods of regression were compared, and the three-parameter nonlinear regression is much more suitable for fitting the grain growth kinetics. A better model with appropriate factors included triangular lattice, the attempted site randomly selected, and the first and second nearest neighbors for energy calculations is obtained.展开更多
A new Monte Carlo simulation method for studying three-dimensional microstructures as well as their evolution in polycrystalline materials has been set up. The algorithm is simple and flexible to apply. With the prese...A new Monte Carlo simulation method for studying three-dimensional microstructures as well as their evolution in polycrystalline materials has been set up. The algorithm is simple and flexible to apply. With the present method, kinetics of three-dimensional grain growth is accurately reflected and the simulation efficiency is greatly improved. The simulation can not only be used reliably to analyze quantitatively the microstructures and their evolution, but also be used conveniently to observe microstructures as well as their evolution on the horizontal section and the sections at any angle to the horizontal plane, to measure the characteristic parameters in three dimensions and cross-sections, together with their relationships between the two systems, and to many other aspects.展开更多
In the present study,we selected solutes to be added to the Cr Co Ni medium-entropy alloy(MEA)based on the mismatch of self-diffusion activation energy(SDQ)between the alloying elements and constituent elements of the...In the present study,we selected solutes to be added to the Cr Co Ni medium-entropy alloy(MEA)based on the mismatch of self-diffusion activation energy(SDQ)between the alloying elements and constituent elements of the matrix,and then investigated their grain growth behavior and mechanical properties.Mo and Al were selected as the solutes for investigation primarily because they have higher and lower SDQ,respectively,than those of the matrix elements;a secondary factor was their higher and lower shear modulus.Their concentrations were fixed at 3 at.%each because previous work had shown these compositions to be single-phase solid solutions with the face-centered cubic structure.Three alloys were produced by arc melting,casting,homogenizing,cold rolling and annealing at various temperatures and times to produce samples with different grain sizes.They were(a)the base alloy Cr Co Ni,(b)the base alloy plus 3 at.%Mo,and(c)the base alloy plus 3 at.%Al.The activation energies for grain growth of the Cr Co Ni,Cr Co Ni-3Mo and CrCo Ni-3Al MEAs were found to be^251,~368 and^219 k J/mol,respectively,consistent with the notion that elements with higher SDQ(in this study Mo)retard grain growth(likely by a solute-drag effect),whereas those with lower values(Al)accelerate grain growth.The roomtemperature tensile properties show that Mo increases the yield strength by^40%but Al addition has a smaller strengthening effect consistent with their relative shear moduli.The yield strength as a function of grain size for the three single-phase MEAs follows the classical Hall-Petch relationship with much higher slopes(>600 MPaμm-0.5)than traditional solid solutions.This work shows that the grain growth kinetics and solid solution strengthening of the Cr Co Ni MEA can be tuned by selecting solute elements that have appropriate diffusion and physical properties.展开更多
基金the International Science & Technology Cooperation Project of Shandong Province(2006)the Natural Science Foundation of Shandong Province(Y2007F06).
文摘The microstructures and their kinetics of normal grain growth are simulated using different Monte Carlo （MC） algorithms. Compared with the relative figures and the theoretical normal grain growth exponents of n =0.5, the effects of some factors of MC algorithm, i.e. the lattice types, the methods of selecting lattice sites, and the neighbors selection for energy calculations, on the simulation results of grain growth are studied. Two methods of regression were compared, and the three-parameter nonlinear regression is much more suitable for fitting the grain growth kinetics. A better model with appropriate factors included triangular lattice, the attempted site randomly selected, and the first and second nearest neighbors for energy calculations is obtained.
文摘A new Monte Carlo simulation method for studying three-dimensional microstructures as well as their evolution in polycrystalline materials has been set up. The algorithm is simple and flexible to apply. With the present method, kinetics of three-dimensional grain growth is accurately reflected and the simulation efficiency is greatly improved. The simulation can not only be used reliably to analyze quantitatively the microstructures and their evolution, but also be used conveniently to observe microstructures as well as their evolution on the horizontal section and the sections at any angle to the horizontal plane, to measure the characteristic parameters in three dimensions and cross-sections, together with their relationships between the two systems, and to many other aspects.
基金the U.S.Department of Energy,Office of Science,Basic Energy Sciences,Materials Sciences and Engineering Division,E.P.Georgethe National Nature Science Foundation of China(No.51971099)+3 种基金the open fund of State Key Laboratory for Advanced Metals and Materials(No.2018-ZD03),X.W.Liuthe National Nature Science Foundation of China(No.51975425),L.C.Zengthe open fund of State Key Laboratory of Materials Processing and Die&Mould Technology(P2019-005),H.Duthe Research and Development Program of Jiangxi Academy of Sciences(No.2020-YZD-23),Q.Hu。
文摘In the present study,we selected solutes to be added to the Cr Co Ni medium-entropy alloy(MEA)based on the mismatch of self-diffusion activation energy(SDQ)between the alloying elements and constituent elements of the matrix,and then investigated their grain growth behavior and mechanical properties.Mo and Al were selected as the solutes for investigation primarily because they have higher and lower SDQ,respectively,than those of the matrix elements;a secondary factor was their higher and lower shear modulus.Their concentrations were fixed at 3 at.%each because previous work had shown these compositions to be single-phase solid solutions with the face-centered cubic structure.Three alloys were produced by arc melting,casting,homogenizing,cold rolling and annealing at various temperatures and times to produce samples with different grain sizes.They were(a)the base alloy Cr Co Ni,(b)the base alloy plus 3 at.%Mo,and(c)the base alloy plus 3 at.%Al.The activation energies for grain growth of the Cr Co Ni,Cr Co Ni-3Mo and CrCo Ni-3Al MEAs were found to be^251,~368 and^219 k J/mol,respectively,consistent with the notion that elements with higher SDQ(in this study Mo)retard grain growth(likely by a solute-drag effect),whereas those with lower values(Al)accelerate grain growth.The roomtemperature tensile properties show that Mo increases the yield strength by^40%but Al addition has a smaller strengthening effect consistent with their relative shear moduli.The yield strength as a function of grain size for the three single-phase MEAs follows the classical Hall-Petch relationship with much higher slopes(>600 MPaμm-0.5)than traditional solid solutions.This work shows that the grain growth kinetics and solid solution strengthening of the Cr Co Ni MEA can be tuned by selecting solute elements that have appropriate diffusion and physical properties.
