The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kine...The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams, which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.展开更多
This work aims at understanding the features of the Sn grains from which whiskers prefe rentially grow.The growth behavior of Sn whiskers on a 50 μm thick hypereutectic Sn-Al alloy coating was observed in situ by map...This work aims at understanding the features of the Sn grains from which whiskers prefe rentially grow.The growth behavior of Sn whiskers on a 50 μm thick hypereutectic Sn-Al alloy coating was observed in situ by mapping the grain orientations before and after aging using the electron backscatter diffraction(EBSD) technique.Sn whiskers were found to grow preferentially from the(001) or near-(001) grains surrounded by the grains having perpendicular orientations,such as(100),(110) and(210).The compre s sive stress in the coating was heterogeneous,and the(001) grains exhibited the higher compressive stress close to the grain boundaries.The orientation relationship between α-Al phase and β-Sn phase was confirmed as(200)_(α-A)||(200)_(β-Sn,[011]_(α-A)||[001]_(β-Sn).The plane matching resulted in approximately0.7 % misfit strain in β-Sn,which had little impact on the growth of whiskers.Dislocations pile-ups were found in the(001) grains and repulsed by the Sn oxide layer,giving the probability of cracking the oxide.Grain boundaries were found between the whisker and underneath grain.The dominant diffusion mode for early whisker growth was grain boundary diffusion aided by pipe diffusion.展开更多
基金Financial supports by the NSFC(China)under the research projects(No.50071058 and No.59725101)by the CAS(China)-CNR(Italy)under an international collaboration agreement are gratefully acknowledged.
文摘The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams, which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.
基金financially supported by the National Natural Science Foundation of China(No.51731004)Zhishan Youth Scholar Program of Southeast University。
文摘This work aims at understanding the features of the Sn grains from which whiskers prefe rentially grow.The growth behavior of Sn whiskers on a 50 μm thick hypereutectic Sn-Al alloy coating was observed in situ by mapping the grain orientations before and after aging using the electron backscatter diffraction(EBSD) technique.Sn whiskers were found to grow preferentially from the(001) or near-(001) grains surrounded by the grains having perpendicular orientations,such as(100),(110) and(210).The compre s sive stress in the coating was heterogeneous,and the(001) grains exhibited the higher compressive stress close to the grain boundaries.The orientation relationship between α-Al phase and β-Sn phase was confirmed as(200)_(α-A)||(200)_(β-Sn,[011]_(α-A)||[001]_(β-Sn).The plane matching resulted in approximately0.7 % misfit strain in β-Sn,which had little impact on the growth of whiskers.Dislocations pile-ups were found in the(001) grains and repulsed by the Sn oxide layer,giving the probability of cracking the oxide.Grain boundaries were found between the whisker and underneath grain.The dominant diffusion mode for early whisker growth was grain boundary diffusion aided by pipe diffusion.
