X-RAY-INVESTIGATION OF SPLAT-COOLED ALLOYS MN-AL AND MN-AL-SI

Both the binary liquid-quenched alloys Mn-Al and the ternary alloys Mn-Al-Si (x(Si) up to 0.5) were prepared using a rotating-wing apparatus. For the X-ray investigation, a Guinier camera with Fe-K-alpha-1 radiation was applied. Although high quenching rates were used, only the low-temperature solid solution beta-Mn(Al,Si) was obtained in manganese-rich alloys. Using liquid quenching for aluminium-rich alloys, the solubility of manganese and silicon in aluminium was extended up to Mn10Al70Si20. Among the phases investigated, the largest range of homogeneity is shown by Mn5(Al,Si)8. The stability of the solid solutions beta-Mn(Al,Si), Al(Mn,Si) and the intermetallic compound Mn5(Al,Si)8 as well of the quasicrystalline phase I-MnAl4 depends mainly on the valence electron concentration. In Guinier photographs of splat-cooled alloys in the concentration range around the ternary phase MnAl2.5Si2.5, an amorphous phase characterized by a broad primary scattering maximum was obtained.