Formation mechanism and growth kinetics of TiAl3 phase in cold-rolled Ti/Al laminated composites during annealing
Jianyu Zhang, Yan-hui WANG, Zheng LÜ, Qing-an CHEN, Yayu Chen, Hezong Li
Abstract
Cold-rolled Ti/Al laminated composites were annealed at 525–625 °C for 0–128 h, and the interfacial microstructure evolution was investigated. The results indicate that only the TiAl3 phase was formed at the Ti/Al interface; most of TiAl3 grains were fine equiaxed with average sizes ranging from hundreds of nanometers to several microns and the TiAl3 grain size increased with increasing annealing time and/or temperature, but the effect of annealing temperature on the TiAl3 grain size was far greater than that of annealing time. The growth of the TiAl3 phase consisted of two stages. The initial stage was governed by chemical reaction with a reaction activation energy of 195.75 kJ/mol, and the reaction rate constant of the TiAl3 phase was larger as the Ti/Al interface was bonded with fresh surfaces. At the second stage, the growth was governed by diffusion, the diffusion activation energy was 33.69 kJ/mol, and the diffusion growth rate constant of the TiAl3 phase was mainly determined by the grain boundary diffusion owing to the smaller TiAl3 grain size.