The internal mechanisms of nucleation and growth of L1_(2)-AI_(3)RE(RE=Sc,Y,La-Lu) second phases in Al alloys were investigated by combining first-principles calculations with quasi-harmonic approximation(QHA).The cal...The internal mechanisms of nucleation and growth of L1_(2)-AI_(3)RE(RE=Sc,Y,La-Lu) second phases in Al alloys were investigated by combining first-principles calculations with quasi-harmonic approximation(QHA).The calculated results show that the diffusion rate D_s and chemical potential AG_V increase with the increase of temperature.With the increase of atomic number,the D_s and the strain energy ΔE_(CS)increase firstly from Sc to La,and then decreases,while the calculated interface energy γ_(α/β) and ΔG_V show opposite tendency.Based on above calculated results,the critical nucleation radius R*and coarsening rate K_(LSW) are obtained from the classical nucleation theory(CNT) and LSW model of the Ostwald ripening of particles,respectively.With the increase of atomic number,the R*increases firstly,and then decreases for all planes at finite temperatures.Whereas the K_(LSW) shows opposite variation to the R^(*).From this point of view,it is reasonably speculated that Y and later RE elements can replace the expensive Sc for heat-resistance Al alloys.The solubility c_(∞) of particles is usually very small at low temperature,and there is obvious solubility only when the temperature reaches 600 K.The surface energies E_(sur) of AI_(3)RE compounds and Al solid solution are respectively larger and smaller than that of pure Al,respectively,except for the surface(001) and(110) of Al_(3)La.For all planes,with the increase of atomic number of RE,E_(sur) decreases firstly from Sc to La,and then increases linearly to Lu.These results are helpful for designing high performance heat-resistance Al alloys.展开更多
Effects of Mn content on mechanical properties of FeCoCrNiMn_(x)(0≤x≤0.3)high-entropy alloys(HEAs)are investigated via first-prmciples calculations combining EMTO-CPA method.Related physical parameters,including lat...Effects of Mn content on mechanical properties of FeCoCrNiMn_(x)(0≤x≤0.3)high-entropy alloys(HEAs)are investigated via first-prmciples calculations combining EMTO-CPA method.Related physical parameters,including lattice constant.elastic constants,elastic modulus,Pugh’s ratio,anisotropy factors,Poisson’s ratio,Cauchy pressure,Vickers hardness,yield strength,and energy factor,are calculated as a function of Mn content.The results show that the resistances to bulk,elastic,and shear deformation decrease with increasing Mn content.Pugh’s ratio B/G indicates that the ductility of FeCoCrNiMn_(x) HEAs has a remarkable reduction between 22 and 24% of Mn content.Meanwhile,Cauchy pressure suggests that the atomic bonding transforms from metallic to directional characteristic from 22 to 24% of Mn content.Vickers hardness and yield strength of FeCoCrNiMn HEA are intrinsically larger than those of FeCoCrNi HEA.Dislocation nucleation easily occurs in FeCoCrNiMn HE A compared to FeCoCrNi HEA,and large dislocation width in FeCoCrNiMnO_(2) HE A results in low stacking-fault energy,which easily induces twinning deformation.This work provides a valuable msieht for further theoretical and experimental study on the mechanical properties of FeCoCrNiMn_(x)(0≤x≤0.3)HEAs.展开更多
Introducing and stabilizing twins in aluminum is a challenge for metals research due to their high formation energy.Employing first-principles calculations,we investigated the twin boundary segregation of alloying ele...Introducing and stabilizing twins in aluminum is a challenge for metals research due to their high formation energy.Employing first-principles calculations,we investigated the twin boundary segregation of alloying elements and their impact on the twin boundary energy in aluminum.Alloying elements with small solubilities but strong interaction with twin boundary would significantly reduce twin boundary energies in aluminum at low temperatures.With increasing temperature,their segregation near twin boundary weakens,leading to their influence on twin boundary energies reduced.Some elements with large solubilities may greatly reduce the twin energies not only at low temperatures but also at high temperatures.Based on careful analysis of charge density and atomic radius,it has been found that chemical difference has little influence on twin boundary energy whereas the atomic size effect plays a leading role in causing the change of twin boundary energy.展开更多
基金Project supported by the R&D plan for Key Areas in Guangdong Province (2020B010186001)the National Natural Science Foundation of China (52171115,52071299)。
文摘The internal mechanisms of nucleation and growth of L1_(2)-AI_(3)RE(RE=Sc,Y,La-Lu) second phases in Al alloys were investigated by combining first-principles calculations with quasi-harmonic approximation(QHA).The calculated results show that the diffusion rate D_s and chemical potential AG_V increase with the increase of temperature.With the increase of atomic number,the D_s and the strain energy ΔE_(CS)increase firstly from Sc to La,and then decreases,while the calculated interface energy γ_(α/β) and ΔG_V show opposite tendency.Based on above calculated results,the critical nucleation radius R*and coarsening rate K_(LSW) are obtained from the classical nucleation theory(CNT) and LSW model of the Ostwald ripening of particles,respectively.With the increase of atomic number,the R*increases firstly,and then decreases for all planes at finite temperatures.Whereas the K_(LSW) shows opposite variation to the R^(*).From this point of view,it is reasonably speculated that Y and later RE elements can replace the expensive Sc for heat-resistance Al alloys.The solubility c_(∞) of particles is usually very small at low temperature,and there is obvious solubility only when the temperature reaches 600 K.The surface energies E_(sur) of AI_(3)RE compounds and Al solid solution are respectively larger and smaller than that of pure Al,respectively,except for the surface(001) and(110) of Al_(3)La.For all planes,with the increase of atomic number of RE,E_(sur) decreases firstly from Sc to La,and then increases linearly to Lu.These results are helpful for designing high performance heat-resistance Al alloys.
基金financially supported by the National Natural Science Foundation of China(No.51501060)China Postdoctoral Science Foundation(No.2018M642973)+5 种基金the State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body at Hunan University(No.31875004)the Key Laboratory of Guangdong Regular Higher Education(No.2017KSYS012)the Foshan Key Technology Project(No.1920001000409)the Guangzhou Technical Project(No.201704030113)the Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110274)the Foshan University Scientifi c Research Project(Nos.CGG07257 and BGH206017)。
文摘Effects of Mn content on mechanical properties of FeCoCrNiMn_(x)(0≤x≤0.3)high-entropy alloys(HEAs)are investigated via first-prmciples calculations combining EMTO-CPA method.Related physical parameters,including lattice constant.elastic constants,elastic modulus,Pugh’s ratio,anisotropy factors,Poisson’s ratio,Cauchy pressure,Vickers hardness,yield strength,and energy factor,are calculated as a function of Mn content.The results show that the resistances to bulk,elastic,and shear deformation decrease with increasing Mn content.Pugh’s ratio B/G indicates that the ductility of FeCoCrNiMn_(x) HEAs has a remarkable reduction between 22 and 24% of Mn content.Meanwhile,Cauchy pressure suggests that the atomic bonding transforms from metallic to directional characteristic from 22 to 24% of Mn content.Vickers hardness and yield strength of FeCoCrNiMn HEA are intrinsically larger than those of FeCoCrNi HEA.Dislocation nucleation easily occurs in FeCoCrNiMn HE A compared to FeCoCrNi HEA,and large dislocation width in FeCoCrNiMnO_(2) HE A results in low stacking-fault energy,which easily induces twinning deformation.This work provides a valuable msieht for further theoretical and experimental study on the mechanical properties of FeCoCrNiMn_(x)(0≤x≤0.3)HEAs.
基金supported financially by the National Natural Science Foundation of China (Nos.51701243,11427806,51471067 and 51371081)the Hunan Provincial Natural Science Foundation of China (No.2019JJ40544)+3 种基金the Specialized Research Found for the Doctoral Program of Higher Education of China (No. 20120161110036)the National Basic Research (973) Program of China (No.2009CB623704)the PhD Research Startup Foundation of Central South University of Forestry and Technology (No. 2017YJ020)the supercomputer TH-1A installed at Hunan University
文摘Introducing and stabilizing twins in aluminum is a challenge for metals research due to their high formation energy.Employing first-principles calculations,we investigated the twin boundary segregation of alloying elements and their impact on the twin boundary energy in aluminum.Alloying elements with small solubilities but strong interaction with twin boundary would significantly reduce twin boundary energies in aluminum at low temperatures.With increasing temperature,their segregation near twin boundary weakens,leading to their influence on twin boundary energies reduced.Some elements with large solubilities may greatly reduce the twin energies not only at low temperatures but also at high temperatures.Based on careful analysis of charge density and atomic radius,it has been found that chemical difference has little influence on twin boundary energy whereas the atomic size effect plays a leading role in causing the change of twin boundary energy.