Ti_3Al-11Nb合金淬火组织中的O相

O-phase in Quenching Structure of Alloy Ti_3Al-11Nb

用TEM和EDS研究了在1040-1120℃加热后水淬的Ti_3Al-11Nb合金热锻棒材样品的组织结构。结果表明,样品组织均由α_2,B2和O相三相组成。O相从形貌上可分为孪晶状和板条状两种。它们的单晶选区电子衍射花样,均可按晶格参数为a=0.6232nm,b=0.9978nm和c=0.4725nm的NaHg结构加以标定。孪晶状O相的成分与α_2相的成分一致。板条状O相的成分中,Nb含量与α_2相的Nb含量相近,而Al含量则较α_2相的Al含量高。孪晶状O相可能是淬火α_2相在应力作用下转变来的。板条状O相组织在形貌上有多种,且随淬火温度降低,在数量上有增加的趋势。它可能是在淬火加热温度就存在,而在淬火过程中保留下来的。淬火组织中3相的数量、形貌及其相互作用显著影响了材料的拉伸性能。

Microstructure of Ti_3Al-11Nb alloy after heating at 1040-1120℃ and water quenching has been investigated by TEM and EDS.It was showed that all microstructure consisted of α_2-,B2-and O-phase.The O-phase could be divided into two types,twin-like and plate-like,according to its morphology.Their single crystal SADPs could be indexed according to a NaHg structure with paramerers of a=0.6232nm,b=0.9978nm and c=0.4725nm.The composition of the twin-like O-phase was identical with the α_2-phase.The Nb content of the plate-like O-phase was near to that of α_2-phase and its Al content was more than that of later. Perhaps,the twin-like O-phase was transformed from quenching α_2-phase under the action of stress.The plate-like O-phase had several types of morphologies and its volume percentage in the structure tended to increase with the decreasing of quenching temperature. Perhaps, it formed in the structure during the quenching heating. Volume percentage, morphology and interaction of α_2-,B2-and O-phase in the structure have obvious effects on the roomtemperature tension property of the alloy.