Precipitation behavior and high strain rate superplasticity in a novel fine-grained aluminum based alloy

摘要

The development of aluminum alloys with superior mechanical properties and high strain rate superplasticity is an important prerequisite for advancing applications of superplastic blow-forming technology. This study focuses on the effect of Ce and Fe additions on the microstructural parameters and tensile properties of a super plastic Al-4.8%Mg-0.6%Mn-0.15%Cr (AA5083-type) alloy. The studied alloy exhibits a bimodal particle size distribution with coarse crystallization origin inclusions and fine secondary precipitates. Both the coarse and fine particles lead to grain refinement. The coarse Ce-, Fe-, and Mn-rich intermetallic particles of crystallization origin provide evidence of a particle-stimulated nucleation effect. The semi-coherent Mn-enriched compact shaped dispersoids with an Ashby-Brown contrast, a quasicrystalline structure, and a mean size of 38 nm are precipitated after low-temperature homogenization and exhibit a strong Zener pinning effect. The proposed thermomechanical treatment results in the development of a grain size of 4 mu m and an ultimate tensile strength of 340 MPa in the recrystallized sheet. The superplastic deformation behavior in a strain rate range of 1 x 10(-2) to 1 x 10(-1) s(-1) and the associated strain-induced changes in the grain structure and mechanical properties of the developed alloy are presented and discussed.