UNIQUE METALLIC-GLASS FORMABILITY AND ULTRA-HIGH TENSILE-STRENGTH IN AL-NI-FE-GD ALLOYS

The metallic glass formability of aluminum-rich Al-Ni-Fe-Gd alloys has been systematically investigated. The critical cooling rate required to form an amorphous state is this system is generally low, and comparable to that of some of the best metallic glass formers, such as Pd-Cu-Si. Amorphous ribbons up to 0.25 mm thick can easily be produced by the single-roller melt-spinning technique. Tensile strengths as high as 1280 MPa and Young's modulus of 75 GPa have been obtained. Bulk amorphous alloys with good mechanical properties are optimized in Al85Ni6Fe3Gd6. DSC and DTA studies reveal that the glass formability is unique for Al-based alloys because the reduced glass temperature T(rg) for Al-Ni-Fe-Gd can be as low as 0.44. This is much lower than conventional theory would suggest for easy glass forming systems. A mechanism for the unusual glass formability is suggested.