冷轧Ti/Al层状复合材料固-液反应过程中的界面微观组织演变

Interfacial Microstructure Evolution During Solid-Liquid Reaction in Cold-Rolled Ti/Al Laminated Composites

摘要:

将冷轧Ti/Al层状复合材料在675~750 ℃下进行不同时间的退火处理，退火过程中钛和铝都保持过剩，研究了Ti/Al层状复合材料的界面微观组织演变。结果表明：Ti和Al的界面层由2个亚层组成，其中一个为紧密的TiAl₃亚层，其微观结构为紧密的TiAl₃层，其中分布着随机取向的充满Al的裂纹，另一个为颗粒状的TiAl₃亚层，其微观组织结构是颗粒状的TiAl₃分布在Al基体中。在不同的退火温度和时间条件下，紧密TiAl₃亚层的厚度几乎没有变化，但是颗粒状亚层的厚度随着退火温度及时间的增加而增加；另外，界面层中的TiAl₃颗粒的体积分数在不同的温度下均随着退火时间的延长而下降。因此提出了反应扩散模型来描述界面层的形成机理，在此模型中，TiAl₃相是化学反应和扩散的结果，并且也考虑了TiAl₃相的溶解。计算结果表明TiAl₃相的形成与生长由化学反应控制，其等效厚度与退火时间之间遵循线性规律，这主要是因为Ti和Al原子能够快速地通过紧密的薄TiAl₃亚层。

Abstract:

Cold-rolled Ti/Al laminated composites were annealed at 675~750 °C for different time with superfluous Ti and Al, and the interfacial microstructure evolution in Ti/Al laminated composites during annealing was investigated. The results indicate that the interfacial layer between Ti and Al consists of two sub-layers: a compact TiAl₃ sub-layer with the microstructure of many randomly oriented cracks filled with Al, and a granular TiAl₃ sub-layer with the microstructure of granular particles distributed in Al matrix. The thickness of the compact TiAl₃ sub-layer is stable at different annealing temperatures for different durations, but the thickness of the granular sub-layer increases with increasing the annealing temperature and duration. Furthermore, the average volume fraction of TiAl₃ phase in the interfacial layer at different temperatures decreases with increasing the duration. A reaction diffusion model, in which the TiAl₃ phase is regarded as the result of diffusion and chemical reaction, was established to evaluate the formation mechanism of the interfacial layer. Additionally, the dissolution of TiAl₃ phase into liquid Al was considered in the model. The calculated results indicate that the formation of TiAl₃ phase is governed by the chemical reaction, and the equivalent thickness of TiAl₃ phase in the interfacial layer obeys a linear relationship with annealing time, which is attributed to the rapid diffusion of Ti and Al atoms through the thin TiAl₃ compact sub-layer.