Effects of Be Additions on Microstructures of TiAl Intermetallic Compounds

First-principles study of Be content on the structural and mechanical properties of TiAl alloy

“…The result is in consistent with the calculation of the TiAl alloys with 5 at.% Be solute by Song et al [28]. No direct information about the site preference of Be in TiAl alloys was given in any experimental reports, except that Nonaka et al [22] found the Ti/Al ratio of ␥ phase increased (the Al content in ␥ phase decreased) by the addition of 0.1 mol% Be. The larger Ti/Al ratio in ␥ phase than that in the stoichiometric composition may indicate the site preference of Be to Al.…”

“…By considering the condition of Be atom substituting for 1-5 Al positions in the supercell, we get a serial TiAl alloys with the Be solute of Ti 12 Al 11 Be, Ti 12 Al 10 Be 2 , Ti 12 Al 9 Be 3 , Ti 12 Al 8 Be 4 , Ti 12 Al 7 Be 5 , and the corresponding Be atomic percent is 4.17, 8.33, 12.51, 16.67 and 20.83 at.%, respectively. The max Be solute (20.83 at.%) is lower than that (29 at.%) of the newly formed compound under 0.6-3 at.% Be addition in experiment [22]. The study of large range effect of Be may help to predict or understand the property variation in the abnormal content accumulated region in the material.…”

“…Therefore, the Be addition to TiAl may cause the decrement of axial c/a ratio and the impurity elements such as oxygen, similar to the Er addition [23]. However, the detailed experimental study of Be effect on microstructures of TiAl intermetallics was only conducted by Nonaka et al [22] using the optical microscopy SEM, EPMA and X-ray diffractometer. They investigated some structural and crystallographic factors availing to the ductility improvements for Ti-Al 0.1-0.3 mol% Be alloys.…”

“…may cause a decrease of the c/a ratio and obtain the ductility improvement. Only a slight attention was paid to the elements close to the Al element (such as C, Si, Be) from both the experimental [22] and theoretical ways [28]. The beryllium element belongs to the IIA group in the periodic table and has strong affinity with oxygen and a chemical active characteristic.…”

“…As for the microstructure control, many methods of stress-induced phase transitions [1][2][3][4][5][6][7][8] were tried to produce the duplex materials, because the two-phase alloys (␥-TiAl + ␣ 2 -Ti 3 Al) were found possessing improved ductility (toughness) than the single phase [9,10]. Meanwhile, the effects of ternary additions on the physical and mechanical properties of TiAl alloys were considered from the experiment [11][12][13][14][15][16][17][18][19][20][21][22][23] and calculation [24][25][26][27][28] aspects. The addition of ternary elements is mainly aimed to influence the binary alloys from three aspects: mechanical properties, oxidation behavior and impurity removing ability.…”