＜正＞In this study,the thermodynamic assessment of the Cd-Mg-Pb ternary system was carried out using the CALPHAD...
Xin RenChangrong LiZhenmin DuCuiping GuoYan Li School of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing 100083China
The effect of the elastic strain energy on the core-shell structures was studied in an Al-0.06Sc-0.02Er (at.%) alloy. A theoretical model for the calculation of the elastic strain energy caused by core-shell precipitates, which is applicable to materials with weak elastic ani-sotropy, was adopted. It was demonstrated that the partitioning of Er to the precipitate core did not reduce the elastic strain energy as expected in the previous study. The resistance due to the elastic strain energy to form an Al3(Sc0.36Er0.64)-Al3(Sc0.8Er0.2) core-shell precipitate was quite small, and could be easily overcome by the decrease of the total interfacial energy, which was consistent with the previous experimental re-sults. On the other hand, the resistance due to the elastic strain energy to form an Al3Er-Al3Sc core-shell precipitate was much larger than that to form an Al3(Sc0.36Er0.64)-Al3(Sc0.8Er0.2) core-shell precipitate, thus the partitioning of all the Er atoms to the core was strongly hindered by the elastic strain energy and was not observed in the experiment of the previous study.)
The as-cast microstructures and solidification paths of the Nb–Si–Ti ternary alloys in the Nb5Si3–Ti5Si3region were investigated.Since there exist some isomorphous compounds in the Nb5Si3–Ti5Si3region,such as aNb5Si3with B3Cr5prototype,bNb5Si3with Si3W5prototype,cNb5Si3with Mn5Si3prototype,and Ti5Si3with Mn5Si3prototype,the primary solidification areas of these compounds were not typically indentified in previous experiments.In the present paper,the microstructure observation,the phase identification,and the composition measurement were performed using scanning electron microscopy(SEM),X-ray diffraction(XRD),and electron probe microanalysis(EPMA),respectively.No ternary compound is found.There exist three primary solidification areas,bNb5-x(Ti)x Si3,aNb5-x(Ti)x Si3,and Ti5-x(Nb)x Si3in the Nb5Si3–Ti5Si3region.Together with the literaturereported experimental data and optimization results,the liquidus projection of the whole Nb–Si–Ti ternary system is constructed,and totally ten primary solidification areas—diamond-Si,Nb1-x(Ti)x Si2,Ti1-x(Nb)x Si2,Ti1-x(Nb)x Si,Ti5-x(Nb)x Si4,bNb5-x(Ti)x Si3,aNb5-x(Ti)x Si3,Ti5-x(Nb)x Si3,(Nb,Ti)3Si,and BCC—and nine transitional invariant reactions—L?Nb1-x(Ti)x Si2?Ti1-x(Nb)x Si2?Si,L?Nb1-x(Ti)x Si2?Ti1-x(Nb)x Si2?Ti5-x(Nb)x Si4,L?Ti5-x(Nb)x Si4?Ti1-x(Nb)x Si2?Ti1-x(Nb)x Si,L?bNb5-x(Ti)5Si3?Nb1-x(Ti)x Si2?Ti5-x(Nb)x Si4,L?bNb5-x(Ti)x Si3?aNb5-x(Ti)x Si3?Ti5-x(Nb)x Si4,L?aNb5-x(Ti)x Si3?Ti5-x(Nb)x Si3?Ti5-x(Nb)x Si4,L?aNb5-x(Ti)x Si3?bNb5-x(Ti)x Si3?Ti5-x(Nb)x Si3,L?bNb5-x(Ti)x Si3?Ti5-x(Nb)x Si3?(Nb,Ti)3Si,and L?(Nb,Ti)3Si?Ti5-x(Nb)x Si3?BCC—are confirmed.
Yan LiChang-Rong LiZhen-Min DuCui-Ping GuoXin-Qing Zhao
Two kinds of experimental methods were tried in the present work:(i)the powder metallurgy method combined with differential thermal analysis(DTA)to determine the metastable liquidus miscibility gap for a Fe–Cu binary system and(ii)the high-temperature melting method combined with isothermal treatment to determine the stable liquidus miscibility gap for a Fe–Sn binary system.The experimental method was adopted according to the characteristics of the liquidus miscibility gap of the specific system.Using the powder metallurgy method,a uniform microstructure morphology and chemical composition was obtained in the DTA specimen,and the phase-separation temperature of the supercooled metastable liquid was measured.The isothermal treatment was applied for the samples inside the stable liquidus miscibility gap;here,equilibrated compositions were reached,and a layered morphology was formed after rapid cooling.The liquid miscibility gaps of the Fe–Cu and Fe–Sn binary systems were measured,and the peak temperatures of the corresponding miscibility gaps were determined to be about 1417°C at x(Cu)=0.465 at%and 1350°C at x(Sn)=0.487 at%,respectively.On the basis of the experimental results,both the Fe–Cu and the Fe–Sn binary systems were thermodynamically assessed.
