Influence of Ga on the formation of phases in cast Al–Mn-based alloys

This work deals with the influence of gallium addition on the constitution and formation of the phases in the Al-rich corner of the Al–Mn system during casting. Al-rich binary Al–Mn and ternary Al–Mn–Ga alloys were cast into a copper mould with a cavity diameter of 5 mm. The microstructures of the produced alloys were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, electron backscatter diffraction and X-ray diffraction. The characterization revealed the presence of αAl, Al6Mn, λ-Al4Mn, L-Al4Mn, icosahedral quasicrystals (IQCs) and decagonal quasicrystals (DQCs). As the amount of gallium in the synthesized alloys increased, the proportion of the phases varied and IQCs and DQCs were formed. Microanalysis revealed that IQCs contained more gallium and less manganese than DQCs. •Binary Al–Mn and ternary Al–Mn–Ga alloys were cast in a copper mould and characterized by SEM, EDS, EBSD and XRD.•Characterization of the alloys shows that αAl, Al6Mn, λ-Al4Mn, L-Al4Mn, IQCs and DQCs are present.•The EDS microanalysis shows that more gallium is present in the IQCs than in the DQCs.•The results reveal that with the addition of gallium to the binary Al–Mn system, L-Al4Mn, IQCs and in some cases DQCs form.