The Influence of Processing Conditions on Microchemistry and the Softening Behavior of Cold Rolled Al-Mn-Fe-Si Alloys

Ning Wang,Yanjun Li,Knut Marthinsen,Ke Huang

doi:10.3390/met6030061

Abstract

Using different homogenization treatments, different initial microchemistry conditions in terms of solid solution levels of Mn, and number densities and sizes of constituents and dispersoids were achieved in an Al-Mn-Fe-Si model alloy. For each homogenized condition, the microchemistry and microstructure, which further change both during deformation and subsequent annealing, were quantitatively characterized. The influence of the different microchemistries, with special focus on different particle structures (constituents and dispersoids), on the softening behavior during annealing after cold rolling and the final grain structure has been systematically studied. Time-Temperature-Transformation diagrams with respect to precipitation and recrystallization as a basis for analysis of the degree of concurrent precipitation during back-annealing have been established. Densely distributed fine pre-existing dispersoids and/or conditions of significant concurrent precipitation strongly slows down recrystallization kinetics and lead to a grain structure of coarse and strongly elongated grains. At the lowest annealing temperatures, recrystallization may even be completely suppressed. In conditions of low number density and coarse pre-existing dispersoids, and limited additional concurrent precipitation, recrystallization generally results in an even, fine and equi-axed grain structure. Rough calculations of recrystallized grain size, assuming particle stimulated nucleation as the main nucleation mechanism, compare well with experimentally measured grain sizes.

Highlights

AA3xxx alloys that contain Mn as a main alloying element have a wide range of applications, e.g., in the building sector, in packaging industry and in equipment for heating and cooling
Four different material conditions, following different homogenization procedures including the as-cast non-homogenized condition of an AlMnFeSi model alloy giving quite different initial microchemistries in terms of content of Mn in solid solution, size and number density of constituent particles as well as dispersoids have been investigated during subsequent cold rolling and back-annealing
It is shown that the softening behavior upon annealing after cold rolling is strongly influenced by the initial microchemistry

Summary

Introduction

AA3xxx alloys that contain Mn as a main alloying element have a wide range of applications, e.g., in the building sector, in packaging industry and in equipment for heating and cooling. It is well known that large particles (larger than about 1 μm) promote recrystallization due to the activation of particle-stimulated nucleation (PSN), and that fine densely distributed dispersoids retard and may even inhibit recrystallization due to the effect of Zener pinning both of low- and high-angle grain boundary motion [5,13,15]. These complex interactions and their influence on the microstructure and texture evolution are still not fully understood and, in particular, adequate quantitative descriptions are still largely missing. More generally the role of dispersoids is of vital importance in the framework of recrystallization induced by severe plastic deformations and the stability of the refined micro- and nanostructure obtained by cold working, with the aim of creating stable grain refined metals with improved properties [16,17]

Results

Discussion

Conclusion