D.G. Ren
,
W.Z. Chen and X.S. Fan ( Laboratory of Atomic Imaging of Solids
,
Institute of Metal Research
,
The Chinese Academy of Sciences
,
Shenyang 110015
,
China
,
College of Materials Science and Engineering
,
Fuzhou University
,
Fuzhou 350002
,
China)
金属学报(英文版)
The microstructures of TiAl intermetallic compounds prepared by ingot metallurgy and centrifugal spray deposition (CSD) were compared by field ion microscopy and atom probe (AP-FIM). The samples used have nearly stoichiometric composition of TiAl but there is Mn addition for ingot metallurgy (IM) samples and Mn and Nb additions for CSD samples. The field ion image of TiAl showed two regions of ordered f.c.t crystal structure (γ-TiAl) and disordered α-Ti3Al, and the distribution of Ti and Al atoms in TiAl alloy showed a lamellar structure which was confirmed by AP profiles. AP profiles showed that the major constituent of IM TiAl alloy is γ-TiAl with some Ti-rich regions. The compositions of these Ti-rich regions are nearly Ti3Al and Ti2Al from the calculation of AP data. The sample of CSD has a similar microstructure as compared with IM sample. The effects of alloying elements (Mn and Nb) on the ordering extent ,their distribution, and their sites occupied in the lattice were explored for both TiAl alloys. But there are no obvious Ti3Al or Ti2Al phases as shown in IM sample. In addition, the distributions of Mn and Nb concentrations in the CSD sample have a characteristic of wave form.
关键词:
intermetallic compound
,
null
,
null
D.G. Ren
,
Z.Q. Li
,
X.S. Fan and J. T. Guo Laboratory of Atomic Imaging of Solids
,
Institute of Metal Research
,
The Chinese Academy of Sciences
,
Shenyang 110015
,
China
金属学报(英文版)
By using AP-FIM the varity of the ordered degree of Ni_3Al with L1_2 structure with B content was studied. The possibility of boron improving ductility was also discussed from bonding between Ni and Al atoms, and antisite defects in Ni_3Al. The extent of ordering is reduced with an increase in boron content and the autisite defects are most obvious for 0.52at.K B-doped sample that has the best ductility. Some results were verified by X-ray diffraction non. The addition of boron not only influences electron environment at grain boundary but also in the interior of Ni_3Al gm ins, the latter is favorable to improve the ductility of Ni_3Al grains.
关键词:
intermetallic compound
,
null
,
null
