In order to study the subboundaries evolution in superplastically deformed NiAl, the positron lifetime change during superplastic deformation process was measured. It is shown that the superplastic deformation of NiAl...In order to study the subboundaries evolution in superplastically deformed NiAl, the positron lifetime change during superplastic deformation process was measured. It is shown that the superplastic deformation of NiAl has not influence on its T2, the newly recrystallized grain boundaries formed during entire superplastic deformation process belong to the calegory of subboundaries and have not contribution to the superplastic strain.展开更多
The defects and electron densities in Ti50AI50, Ti50Al48Mn2 and Ti50Al48Cu2 alloys have been studied by positron lifetime measurements. The results show that the free electron density in the bulk of binary TiAl allov ...The defects and electron densities in Ti50AI50, Ti50Al48Mn2 and Ti50Al48Cu2 alloys have been studied by positron lifetime measurements. The results show that the free electron density in the bulk of binary TiAl allov is lower than that of pure Ti or Al metal. The open volume of defects on the grain boundaries of binary TiAl alloy is larger than that of a monovacancy of Al metal. The additions of Mn and Cu into Ti-rich TiAl alloy will increase the free electron densities in the bulk and the grain boundary simultaneously, since one Mn atom or Cu atom which occupies the Al atom site provides more free electrons participating metallic bonds than those provided by an Al atom. It is also found the free electron density in the grain boundary of Ti50Al48Cu2 is higher than that of Ti50Al48Mn2 alloy, while the free electron density in the bulk of Ti50AI48Cu2 is lower than that of Ti50Al48Mn2 alloy. The behaviors of Mn and Cu atoms in TiAl alloy have been discussed.展开更多
基金the National Natural Science Foundation of China(contract No.59895152 and 59801010)National Advanced Materials Committee of China(No.863-715-0030)for their financial supports.
文摘In order to study the subboundaries evolution in superplastically deformed NiAl, the positron lifetime change during superplastic deformation process was measured. It is shown that the superplastic deformation of NiAl has not influence on its T2, the newly recrystallized grain boundaries formed during entire superplastic deformation process belong to the calegory of subboundaries and have not contribution to the superplastic strain.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59881003) and the Science and Technology Foundation of Guangxi Personnel Department.
文摘The defects and electron densities in Ti50AI50, Ti50Al48Mn2 and Ti50Al48Cu2 alloys have been studied by positron lifetime measurements. The results show that the free electron density in the bulk of binary TiAl allov is lower than that of pure Ti or Al metal. The open volume of defects on the grain boundaries of binary TiAl alloy is larger than that of a monovacancy of Al metal. The additions of Mn and Cu into Ti-rich TiAl alloy will increase the free electron densities in the bulk and the grain boundary simultaneously, since one Mn atom or Cu atom which occupies the Al atom site provides more free electrons participating metallic bonds than those provided by an Al atom. It is also found the free electron density in the grain boundary of Ti50Al48Cu2 is higher than that of Ti50Al48Mn2 alloy, while the free electron density in the bulk of Ti50AI48Cu2 is lower than that of Ti50Al48Mn2 alloy. The behaviors of Mn and Cu atoms in TiAl alloy have been discussed.
