Chemical randomness and the associated energy fluctuation are essential features of multi-principal ele-ment alloys(MPEAs).Due to these features,nanoscale stacking fault energy(SFE)fluctuation is a natural and indepen...Chemical randomness and the associated energy fluctuation are essential features of multi-principal ele-ment alloys(MPEAs).Due to these features,nanoscale stacking fault energy(SFE)fluctuation is a natural and independent contribution to strengthening MPEAs.However,existing models for conventional alloys(i.e.,alloys with one principal element)cannot be applied to MPEAs.The extreme values of SFEs required by such models are unknown for MPEAs,which need to calculate the nanoscale volume relevant to the SFE fluctuation.In the present work,we developed an analytic model to evaluate the strengthening ef-fect through the SFE fluctuation,profuse in MPEAs.The model has no adjustable parameters,and all parameters can be determined from experiments and ab initio calculations.This model explains available experimental observations and provides insightful guidance for designing new MPEAs based on the SFE fluctuation.It generally applies to MPEAs in random states and with chemical short-range order.展开更多
The empirical rules for the prediction of solid solution formation proposed so far in the literature usually have very compromised predictability.Some rules with seemingly good predictability were,however,tested using...The empirical rules for the prediction of solid solution formation proposed so far in the literature usually have very compromised predictability.Some rules with seemingly good predictability were,however,tested using small data sets.Based on an unprecedented large dataset containing 1252 multicomponent alloys,machine-learning methods showed that the formation of solid solutions can be very accurately predicted(93%).The machine-learning results help identify the most important features,such as molar volume,bulk modulus,and melting temperature.展开更多
We have investigated twin boundaries in double-lattice hexagonal close-packed metallic materials,focusing on their atomic geometry.Combining accurate ab-initio methods and large-scale atomistic simulations we address ...We have investigated twin boundaries in double-lattice hexagonal close-packed metallic materials,focusing on their atomic geometry.Combining accurate ab-initio methods and large-scale atomistic simulations we address the following two fundamental questions:(i)What are the possible intrinsic twin boundary structures in hcp crystals?(ii)Are these structures stable against small distortions?In order to help end a decade-long controversy over the experimental observations of the atomic structures of twin boundaries,we have determined the energetics,spectra,and transition mechanisms of the twin boundaries.Our results confirm that the mechanical stability controls structures which are observed.展开更多
We study the K-state phenomenon in the NiCoCr medium-entropy alloy using first-principles techniques jointly with the efficient Wang–Landau Monte Carlo and simulated annealing algorithms.Our theoretical results succe...We study the K-state phenomenon in the NiCoCr medium-entropy alloy using first-principles techniques jointly with the efficient Wang–Landau Monte Carlo and simulated annealing algorithms.Our theoretical results successfully explain the existence of the peak around 940 K in the experimental specific heat curve that characterizes the K-state phenomenon and give a fine picture of its atomic origin.The peak is caused by the maximum change of the local configurations characterized by the short-range-order(SRO)parameters at that temperature.展开更多
基金sponsored by the U.S.Department of En-ergy,Office of Science,Basic Energy Sciences,Materials Science and Engineering Divisionsupported by the Office of Science of the U.S.Department of Energy under Contract No.DE-AC05-00OR22725+2 种基金the supports from(1)the National Science Foundation(DMR-1611180 and 1809640)with program directors,Drs.J.Yang,G.Shifletthe US Army Research Office(W911NF-13-1-0438 and W911NF-19-2-0049)with program managers,Drs.M.P.Bakas,S.N.Math-audhuthe support of U.S.Na-tional Science Foundation under grant DMR-1804320.
文摘Chemical randomness and the associated energy fluctuation are essential features of multi-principal ele-ment alloys(MPEAs).Due to these features,nanoscale stacking fault energy(SFE)fluctuation is a natural and independent contribution to strengthening MPEAs.However,existing models for conventional alloys(i.e.,alloys with one principal element)cannot be applied to MPEAs.The extreme values of SFEs required by such models are unknown for MPEAs,which need to calculate the nanoscale volume relevant to the SFE fluctuation.In the present work,we developed an analytic model to evaluate the strengthening ef-fect through the SFE fluctuation,profuse in MPEAs.The model has no adjustable parameters,and all parameters can be determined from experiments and ab initio calculations.This model explains available experimental observations and provides insightful guidance for designing new MPEAs based on the SFE fluctuation.It generally applies to MPEAs in random states and with chemical short-range order.
基金Research performed by Leidos Research Support Team staff was conducted under the RSS contract 89243318CFE000003This research was supported in part by an appointment to the U.S.Department of Energy(DOE)Postgraduate Research Program at the National Energy Technology Laboratory(NETL)administered by the Oak Ridge Institute for Science and EducationThis research used resources of Oak Ridge National Laboratory’s Compute and Data Environment for Science(CADES)and the Oak Ridge Leadership Computing Facility,which is supported by the Office of Science of the U.S.Department of Energy under Contract No.DE-AC05-00OR22725.
文摘The empirical rules for the prediction of solid solution formation proposed so far in the literature usually have very compromised predictability.Some rules with seemingly good predictability were,however,tested using small data sets.Based on an unprecedented large dataset containing 1252 multicomponent alloys,machine-learning methods showed that the formation of solid solutions can be very accurately predicted(93%).The machine-learning results help identify the most important features,such as molar volume,bulk modulus,and melting temperature.
基金the financial supports of the Max-Planck Society at the Max-Planck-Institut fur Eisenforschung GmbH.the support from the Academy of Sciences of the Czech Republic through the Fellowship of J.E.Purkyne.
文摘We have investigated twin boundaries in double-lattice hexagonal close-packed metallic materials,focusing on their atomic geometry.Combining accurate ab-initio methods and large-scale atomistic simulations we address the following two fundamental questions:(i)What are the possible intrinsic twin boundary structures in hcp crystals?(ii)Are these structures stable against small distortions?In order to help end a decade-long controversy over the experimental observations of the atomic structures of twin boundaries,we have determined the energetics,spectra,and transition mechanisms of the twin boundaries.Our results confirm that the mechanical stability controls structures which are observed.
基金This research used resources of the Oak Ridge Leadership Computing Facility,which is supported by the Office of Science of the U.S.Department of Energy under Contract No.DE-AC05-00OR22725M.C.G.acknowledges the support of the US Department of Energy’s Fossil Energy Crosscutting Technology Research Program at National Energy Technology Laboratory under the RSS contract 89243318CFE000003.
文摘We study the K-state phenomenon in the NiCoCr medium-entropy alloy using first-principles techniques jointly with the efficient Wang–Landau Monte Carlo and simulated annealing algorithms.Our theoretical results successfully explain the existence of the peak around 940 K in the experimental specific heat curve that characterizes the K-state phenomenon and give a fine picture of its atomic origin.The peak is caused by the maximum change of the local configurations characterized by the short-range-order(SRO)parameters at that temperature.
