Tuning the microstructure features of in-situ nano TiB2/Al-Cu-Mg composites to enhance mechanical properties

Abstract

In the in-situ TiB2/Al-Cu-Mg composite, the dislocations are non-uniformly distributed after solution treatment, where the localized dislocations with the higher densities around TiB2 particles have induced the heterogeneous precipitation of S(Al2CuMg) phases and formed precipitation free zones (PFZs) during the aging process. These microstructure features have induced the inhomogeneously aging response on the age hardening process, and strongly limited the further increment of mechanical properties of the composite. It has thus indicated the conventional aging treatment is inappropriate for the TiB2/Al-Cu-Mg composite. In this work, we have introduced uniform dislocations into the composite prior to artificial aging by the pre-stretch method. Resultantly, the S precipitates can be refined to precipitate uniformly, and the PFZs have been successfully eliminated through the aging treatment. Based on these improved microstructure features, the homogeneous aging behavior has been achieved, and the strength and ductility are simultaneously enhanced for TiB2/Al-Cu-Mg composites. The underlying mechanisms related to the superior strength-ductility combination have been discussed in terms of microstructure characteristics in the composite.