Microstructure characterization of melt spun Mg65Cu225Y10

Abstract

Mg65Cu25Y10 ribbons were produced by melt spinning. Their microstructure was investigated in its as-cast condition, after pressing under 0.5 GPa for 5 min under different temperatures -RT, 50, 100, 150, and 200• C -and after five-minute exposure to the above temperatures without pressing. The microstructure was characterized by means of XRD, DSC, HRSEM, and HRTEM. XRD and DSC studies showed that the as-cast material had an amorphous character and that the material crystallized during exposure to temperature with or without applying stress. HRTEM revealed that the as-cast Mg65Cu25Y10, although known to be one of the best glass formers, is nano-crystalline rather than amorphous.K e y w o r d s : microstructure, melt spinning, metallic glass, Mg65Cu25Y10

Quantitative microstructure study of melt-spun Mg65Cu25Y10

“…According to XRD and DSC, the as-cast melt-spun Mg 65 Cu 25 Y 10 seems to be amorphous, while clear nano-grains were observed by means of HRTEM. As proposed elsewhere by Regev et al [24], the contribution of the grain boundaries, which are amorphous by definition, is responsible for the amorphous character of the XRD spectrum. Tables 2 and 3 show that serious errors may occur when regarding the as-cast meltspun Mg 65 Cu 25 Y 10 as completely amorphous.…”

“…6a, supports this claim. Other examples of single nano-grains have been already published elsewhere [24]. Examination of a few tens of nano-grains leads to the estimation that the average grain size of the as-cast material is about 8 nm, while the width of the grain boundary region is about 2 nm (10-15 times the magnesium lattice parameter).…”

“…In a previous study by Regev et al [24], high-resolution transmission electron microscopy (HRTEM) as well as other characterization tools, namely, XRD, DSC and high-resolution scanning electron microscope (HRSEM), were applied in order to study the amorphous nature of melt-spun Mg 65 Cu 25 Y 10 . This study [24] also included XRD (1) ΔT x = T x − T g investigations of Mg 65 Cu 25 Y 10 after 5-minute exposure to 50 °C, 100 °C, 150 °C and 200 °C. The study found that the material lost its amorphous character upon exposure to temperature; however, this conclusion was based solely on XRD peak identification without any quantitative analysis.…”