Abstract
The effects of solute element content and cooling rate on the morphology of Al6Mn phase in suction casting Al–Mn alloys were investigated by transmission electron microscope, scanning electron microscope, and X-ray diffractometer. Results show that Al6Mn dendrite morphology with different degrees of development can occur in the microstructure of as-cast Al–Mn alloys. For the Al–4 wt.% Mn alloy, there are small amounts of block Al6Mn crystals at the center of sample, while we see a block Al6Mn phase and a feathery Al6Mn phase in the sample of Al–6 wt.% Mn alloy. Moreover, the block Al6Mn phases in the Al–8 wt.% Mn alloy disappear, and only snowflake-like Al6Mn phases play a dominant role in the microstructure. However, with an increase in Mn content to 10 wt.%, more dendritic trunks are formed, and secondary dendrite arms are degraded more seriously due to the formation of an icosahedral quasicrystal in suction casting. In addition to the effect of Mn content on Al6Mn morphology, with the increase in cooling rate from the center to the edge of samples, the outline diameter of equiaxed dendrite decreases. The evolution of Al6Mn dendrite morphology and the formation of quasicrystal are further discussed.
Highlights
As we all know, for the alloys with excellent mechanical properties, a good solidification structure is essential
Al–Mn alloy with an Mn content up to 1.5 wt.% has sufficient strength, good corrosion resistance, and excellent formability and weldability, allowing it to become the first choice of packaging and architectural application [2]
The crystal structure was identified by an X-ray diffractometer (XRD, X0 Pert PRO MPD, Almemo, Holland) with Cu Kα radiation operating at 40 kV/35 mA and diffractions in the 2θ range from 25◦ to 80◦
Summary
For the alloys with excellent mechanical properties, a good solidification structure is essential. According to the strict control of the microstructure formed, the mechanical properties of aluminum alloys can be enhanced by up to 20% during the casting process [1]. Al–Mn alloy with an Mn content up to 1.5 wt.% has sufficient strength, good corrosion resistance, and excellent formability and weldability, allowing it to become the first choice of packaging and architectural application [2]. The Mn element content of widely used Al–Mn alloys in industry is generally between 1.0 wt.% and 1.6 wt.%, mainly because the solid solubility of Mn in α-Al is only 1.8 wt.% at 65 ◦ C [3]. Looking for an easy way to amend such a conflict of strength and ductility remains a key issue
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