超温处理对精密铸造Ti2AlNb合金组织及性能的影响

Influence of Overtemperature Treatment on Microstructure and Properties of Precision-Cast Ti2AlNb Alloy

摘要:

采用光学显微镜、扫描电子显微镜研究了精密铸造Ti₂AlNb合金在750和850 ℃下超温处理后的组织演变，并使用Image J金相分析软件进行定量分析，同时测试了超温前后的力学性能变化。结果表明：Ti₂AlNb合金超温前后均由B2相和O相板条组成；超温处理后，部分B2相转变为O相，且O相板条组织发生不连续粗化和球化，粗化程度随着超温温度的增加和超温时间的延长而加重，O相含量也逐渐增加；Ti₂AlNb合金的显微硬度与室温、高温拉伸性能均随着超温温度的增加和超温时间的延长而下降，且高温抗拉伸强度下降幅度更大；显微硬度与O相含量间存在显著线性关联，O相含量及显微硬度均是表征Ti₂AlNb合金超温服役损伤程度的关键参量。

Abstract:

Microstructure evolution of precision-cast Ti₂AlNb alloys after overtemperature treatments at 750 and 850 °C was investigated by optical microscope and scanning electron microscope, and Image J metallurgy analysis software was used for quantitative analysis. The variation of mechanical properties before and after overtemperature treatment was tested. Results show that the Ti₂AlNb alloy consists of B2 phase and lamellar O phase before and after overtemperature treatment. After overtemperature treatment, partial B2 phase is transformed into the O phase, and the lamellar structure of O phase suffers discontinuous coarsening and spherolization. The coarsening degree is increased with the increase in temperature and prolongation of treatment time, and O phase content is also gradually increased. The microhardness and tensile properties of Ti₂AlNb alloys at room and high temperatures are decreased with the increase in temperature and prolongation of treatment time, and the high-temperature tensile strength exhibits relatively larger decrement. An obvious linear relationship exists between microhardness and O phase content. Both the microhardness and the O phase content are important parameters to evaluate the overtemperature service damage degree of precision-cast Ti₂AlNb alloy.