Microstructure control of TiAl alloys containing β stabilizers by directional solidification
Microstructure control of TiAl alloys containing β stabilizers by directional solidification
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DOI：
10.1016/s0921-5093(01)01494-0
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发表时间：
2002-06
期刊：
影响因子：
6.4
通讯作者：
In-Soo Jung;Hs Jang;M. Oh;J. Lee;D. Wee
中科院分区：
文献类型：
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作者：
In-Soo Jung;Hs Jang;M. Oh;J. Lee;D. Wee
通过对钛合金弧熔球枝晶形貌的分析，研究了Ti-Al-X（X=Mo，Re，W）系合金的高温相变。结果表明，Mo、Re和W等β稳定剂的加入使固液温度下的β相区向高Al成分侧移动。因此，在Ti-Al-X三元系中，即使Al含量比Ti-Al二元系高，β相仍以初生相形式存在。在Mo、Re、W中，W是最有效的β（bcc）稳定剂，Ti-47 Al-2 W合金为β凝固合金。在Bridgman定向凝固装置上以90 mm/h的生长速率对Ti-47 Al-2 W合金进行定向凝固时，发现柱状晶中的片层取向与生长方向平行或倾斜45°。这意味着Ti-47 Al-2 W合金中β相在固/液界面处形成。在保持相同屈服应力水平的情况下，定向凝固合金的拉伸伸长率明显高于具有完全层状组织的多晶合金。
Phase transformation at elevated temperatures in Ti-Al-X(X=Mo, Re, W) systems has been investigated by analyzing the dendrite morphology of arc-melted buttons. It was found that the addition of β stabilizers, such as Mo, Re and W, shifted the β phase field at liquid/solid temperatures to the high Al composition side. So, the β phase formed as a primary crystal even in higher Al compositions in Ti-Al-X ternary systems compared with Ti-Al binary. The addition of W was found to be the most effective β (bcc) stabilizer among Mo, Re, W, and the Ti-47Al-2W composition was selected for β solidification. In the directional solidification of Ti-47Al-2W alloy at the growth rate of 90 mm/h using the Bridgman type DS apparatus, it was found that the lamellar orientation in the columnar grains was parallel or inclined with the angle of 45° to the growth direction. This means that the β phase forms at the solid/liquid interface in the Ti-47Al-2W alloy. The tensile elongation of DS alloys was clearly improved compared with that of the polycrystalline alloy with a fully lamellar microstructure, while maintaining the same yield stress level.