Enhanced aging kinetic of Al3BC/6061 Al composites and its micro-mechanism

In this work, the aging behavior of Al3BC/6061 Al composites was investigated and the impacts of Al3BC on the aging kinetic as well as its micro-mechanism were unveiled. It is found that the aging kinetic of the composites is considerably accelerated and the peak aging time at 175 degrees C comes down from 14 to 6 h. Both positive and negative impacts due to the incorporation of Al3BC on the aging kinetic of the composites were discussed. The high density dislocations can either act as the heterogeneous nucleation substrate or play as the diffusion path to expedite precipitation process, while the low vacancy concentration and solute segregation on the interface suppress the formation of GP zone and reduce the chemical driving force for precipitation, respectively. Obviously, the positive effects caused by the dislocation contribute more in the current work. Microstructure characterizations verify that needle-like beta '' phase and lath Q' phase precipitate in the matrix and are impacted by the Al3BC differently. In the area free of Al3BC particle, they distributed uniformly in the matrix. However, in the vicinity of Al3BC particles, the precipitation of beta '' is inhibited for the low vacancy concentration and segregation of Mg, Si elements on the Al3BC/Al interface, while the precipitation of Q' phase is accelerated for the preferred nucleation of Q' phase on the dislocation. (C) 2017 Published by Elsevier B.V.