Evolution of Fe-Bearing Phases During the Fabrication and its Effect on the Mechanical Properties of Aa8014 Aluminum Alloy

Abstract

The morphology of Fe-bearing phase particles has significant effects on the mechanical properties of AA8014 aluminum alloy sheets. It is important to study the evolution of the morphology, size, and distribution of Fe-bearing phases through casting, homogenization, and rolling. In the paper, the effect of thermal treatment and deformation on the evolution of the Fe-bearing phases, and the mechanical properties of AA8014 aluminum alloy annealing sheet have been studied quantitatively. The main phase components in the DC-cast ingot are α-Al matrix, Al6(Fe,Mn), and a small amount of Al3(Fe,Mn) and α-Al(Fe,Mn)Si. During homogenization at 630°C for 12 hours, the metastable Al6(Fe,Mn) particles transformed to stable α-Al(Fe,Mn)Si with “pore structures”. After hot rolled to a sheet with 7 mm thickness, the area number density of the Fe-bearing particles increases significantly, the average length and aspect ratio decreases significantly, and the distribution of the Fe-bearing phases is more uniform. After cold rolled to a sheet with 0.7 mm thickness, or further annealing, the area number density, and size of the Fe-bearing phases changes slightly. The content of α-Al(Fe,Mn)Si is very low in the non-homogenized ingot, after hot rolling and cold rolling, there are coarse Fe-bearing particles in a hot-rolled sheet with 7 mm thickness and cold-rolled sheet with 0.7 mm thickness, and the distribution of the Fe-bearing phases is nonuniform. A comparative study was conducted on the mechanical properties and microstructure in final sheets with 0.7 mm thickness fabricated from non-homogenization and homogenization. The yield strength, ultimate tensile strength, elongation, and work hardening exponent in sheet with homogenization are higher, due to fine grain size and refined Fe-bearing phases, due to smaller grain and Fe-bearing phase particles.

Keywords: AA8014 aluminum alloy, Fe-bearing phases, Homogenization, Hot rolling, Cold rolling, mechanical property