Synthesis of nanocrystalline/quasicrystalline Mg₃₂(Al,Zn)₄₉ by melt spinning and mechanical milling

Abstract

In the present investigation we have made an attempt to synthesize T-Mg₃₂(Al,Zn)₄₉ Frank Kasper phase and investigate the mechanical properties of the T-Phase in micro and nano scale. Single T-Phase (bcc, a = 1.42 nm) has been prepared by conventional casting with a proper combination of flux in order to avoid the loss of magnesium from the melt. Chemical analysis by energy dispersive X-ray microanalysis system attached to scanning electron microscope has confirmed the desired composition for T-phase. The as-cast material was then rapidly solidified by melt spinning and mechanically milled using a high-energy ball mill. The samples were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction techniques. The rapidly solidified foils showed the presence of mostly nanoquasicrystalline phases coexisting with a minute amount of crystalline phases in the thin region where the cooling rate is expected to be high. The dark field imaging in electron microscopy clearly confirms the existence of nano phases. Mechanically milled powder exhibited the evolution of nanophases at higher milling time. Microhardness measurement at low load was carried out in both the as-cast and nanophase materials in order to understand the influence of nanophases on the mode of deformation and cracking at low load.