Microstructural evolution, strengthening and toughening mechanisms of AZ80 composite sheet reinforced by TiB2 with fiber-like distribution

In-situ TiB2/AZ80 composite was prepared by a simple casting method, and then hot-rolling. Effects of TiB2 reinforcements on the microstructural evolution of composite were investigated. In-situ TiB2 particles could refine the as-cast grains of AZ80 alloy, and promote recrystallization through particle stimulated nucleation (PSN) effect. Due to the grain refinement and the PSN effect of TiB2, the twin induced recrystallization mode in AZ80 alloy is transformed into grain boundary and particle dominated recrystallization process in the TiB2/AZ80 composite, which suppresses the generation of coarse shear bands during rolling and improves the rolling ability. At the same time, the morphology of TiB2 particle clusters was continuously modified with the increase of rolling passes, and finally formed fiber-like distribution characteristics. Fine grain strengthening and thermal mismatch strengthening are the main strengthening mechanisms of the composite sheet. Internal toughening mechanisms are texture weakening, the proliferation of more < c+a > dislocations, higher Schmidt factor and more uniform strain distribution induced by the PSN effect. In addition, external toughening ones should attribute to bending and deflection of cracks resulting from fiber like particle distribution characteristics. Thus, the strength and toughness of the TiB2/AZ80 composite were simultaneously enhanced. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The in-situ TiB2/AZ80 composite was prepared by a simple casting method and hot-rolling, which showed improved strength and toughness. The TiB2 particles can refine the grains of AZ80 alloy and promote recrystallization through PSN effect, leading to a transformation in recrystallization mode and distribution characteristics of TiB2 particle clusters. The composite sheet mainly gains strength from fine grain strengthening and thermal mismatch strengthening, while internal toughening mechanisms include texture weakening and the proliferation of more dislocations induced by the PSN effect. External toughening mechanisms are attributed to bending and deflection of cracks resulting from fiber-like particle distribution characteristics.