TiAl基合金在快速加热循环热处理过程中的结构失稳

Microstructural Instability of A TiAl-Based Alloy during Rapid Heating Cyclic Heat Treatment

摘要:

观察了快速加热循环热处理过程中发生的4种结构失稳现象：形成二次层片组织、原始层片球化、晶界处非连续粗化、相界形核。通过比较连续加热与等温加热条件下的相转变开始线，探讨了连续加热与等温加热条件下结构失稳机制的异同。提出了快速加热循环热处理过程中避免结构失稳的途径：确保合金成分均匀，使各区域相变温度一致；使最高温度下的保温时间尽可能短。

Abstract:

Four kinds of microstructural instability of a TiAl-based alloy during rapid heating cyclic heat treatment were observed: (i) the formation of secondary lamellae, (ii) the spheroidization of primary lamellae, (iii) a discontinuous coarsening at grain boundaries and (iv) nucleation at phase interfaces. By comparing the starting line of continuous heating transformation with that of TTT diagram, the similarity and difference of the microstructure instability during continuous heating and isothermal heating conditions were studied. Ways of avoiding unfavorable microstructural instability were proposed such as: (i) insuring homogeneity of the composition so as to guarantee the identity of transformation temperature in the alloy; (ii) holding at the highest temperature for as short a time as possible.