| Mg65Cu25Gd10(at.%) bulk metallic glass with a diameter of 3 mm was prepared by injection casting. Microstructure, thermal properties and fracture surface morphology were studied by XRD, DSC and SEM. The effect of annealing on the amorphous alloys under nanoindentation and the dependence of temperature and strain rate on the mechanical properties were also studied.At room temperature , the strain rates in this study have no obvious effect on the strength of Mg65Cu25Gd10 metallic glass. The strength at room temperature in this study is determined to be 785±40 MPa. The fracture surface containes three parts, i.e., river-like zone, hackle zone and lubricous zone. The hackle zone characterizes dimple structure in micro-scale, and lubricous zone periodic corrugations; the wavelength of corrugations changes little at low strain rates and decreases when the strain rate increases to 1×10-1 s-1.Annealing affects the deformation of bulk metallic glass under nanoindentation. The steps of loading curves of as-annealed alloys are narrower than that of as-cast amorphous alloys. With the increase of annealing time, the steps of loading curves become borader first and then narrower. The nucleation and propagation of shear bands play an important role in the mechanical properties of amorphous alloys under nanoindentation.The deformation of Mg65Cu25Gd10 bulk metallic glass is very sensitive to strain rate and testing temperature in the supercooled liquid region. At a given temperature and strain rate, the amorphous alloys deforms elasticly at first, and the stress increases to its maximum followed by decreasing to a steady value.The peak stress increases with increasing strain rate and decreases with increasing temperature. The deformtaion in the supercooled liquid region corresponds to a transformation from non-Newton fluid to Newton- fluid. At high temperatures, the viscosity changes little with increasing temperatures, indicating a better plasticity. Crystallization occurs at a deformation temperature higher than Tx, and the bulk metallic glass fracture along the boundries of the crystals.At low temperature, the compression strength changes little when the strain rate changes from 1.3×10-3 s-1 to 4.0×10-3 s-1 and decreases instantly when the strain rate increases to 1×10-3 s-1. The fracture surface is simliar to that of room temperature. The wavelengthes of periodic corrugations on the fracture surface decreases with the increase of strain rate at low temperature. The strength decreases instantly with increaing temperature near Tg, due to the instant increase of free volume at the temperatures near Tg.
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