Effect of Changing Homogenization Treatment on the Particle Structure in Mn-Containing Aluminium Alloys

Abstract

During casting and homogenisation of aluminium the microstructural fundament for further processing is made. Particle structure (dispersoids and primary particles), grain structure and level of elements in solid solution govern the mechanical and annealing properties of the material. In 3xxx-alloys, Mn in solid solution and Mn-containing dispersoids formed during homogenisation play an important role in controlling the recrystallization behaviour of the material [e.g. 1, 2, 3]. Other elements, such as Si, will have an influence on the formation of dispersoids [4, 5]. Hence, to control the annealing behaviour of the material, it becomes important to control the particle structure. In the present investigation, an AA3103 alloy, and modified versions of this alloy, have been investigated. Various homogenisation treatments have been performed and the resulting material has been studied. Electrical conductivity has been measured and microstructural investigations have been carried out.

Characterization of the Density and Spatial Distribution of Dispersoids in Al-Mg-Si Alloys

“…Here, the dispersoid density was higher for lower heating rates. This expectation was based on earlier studies, which showed an increase in dispersoid number densities with decreasing homogenization temperatures [10,22]. Such a relation suggests that the amount of time spent at lower temperatures could lead to an increase in number density.…”

“…This may cause the results to vary greatly with the operator on duty. Such evaluations of dispersoid distributions may, for example, be done by measuring the width of the dispersoid-free zones (DFZs) [9], or measuring the change in density from the grain boundary towards the center of the grain [10]. These methods are time consuming and may be inaccurate and inadequate.…”

Improving Elevated-Temperature Strength of an Al–Mn–Si Alloy by Strain-Induced Precipitation

“…The string-like distribution is probably due to heterogeneous precipitation on dislocations, which was also observed in ref. [6]. The TEM and SEM images (Figures 2 and 3) show that the distribution of dispersoids in the rolled sample is homogeneous due to the high-density dislocations and sub-boundaries.…”

“…However, the dispersoids precipitated during the heat treatment of as-cast Al-Mn are heterogeneously distributed due to micro-segregation in the as-cast structure. It has been observed that the number density of dispersoids at the center of the dendrite arm was significantly lower than that in the periphery of the dendrite arm [6].…”

“…Dispersion hardened Al-Mn alloys are suggested for potential applications at elevated temperatures. Extensive investigations are reported on the precipitation of dispersoids in Al-Mn alloys [3][4][5][6][7][8]. It is reported that Al6Mn is the dominate phase in binary Al-Mn alloys, and α-AlMnSi becomes the dominate phase in Al-Mn-Si with a high content of Si [3,4].…”