Dynamics of the strong metallic glass Zn38Mg12Ca32Yb18

Abstract

Zn38Mg12Ca32Yb18 bulk metallic glass (BMG) presents higher corrosion resistance, lower glass transition temperature and lower density than most BMGs. Dynamic properties of Zn38Mg12Ca32Yb18 BMG were investigated by mechanical spectroscopy. The structural (α) process in the isothermal spectra is well described by a Kohlrausch-Williams-Watts (KWW) function with βKWW=0.505. At high frequency, an extra contribution to the α process (i.e. an excess wing) is observed with a much smaller frequency dependence of the loss shear modulus G″(f)~f−0.37, indicating the presence of a submerged secondary peak. The temperature behaviour of the α relaxation time, τα, is characterized by a very small steepness index (i.e. strong behaviour). We find that results for this BMG show a deviation of the correlation between fragility and βKWW generally found in glass formers. Results in the literature for other BMGs suggest that this deviation may not be an exception for BMGs, since very similar values of βKWW (~0.5) have been found for BMGs independently of their steepness index.