SYNTHESIS AND PROPERTIES OF ALUMINUM-BASED METALLIC GLASSES CONTAINING RARE-EARTHS

A new family of metallic glasses containing up to 92 at.% of aluminum has been synthesized in Al-TM-RE (where TM = transition metals, RE = y ttrium and rare earths) alloy systems using a melt-spinning technique. The atomic structure, mechanical properties, thermal and mechanical s tability of these metallic glasses have been studied. Structural studi es by pulsed neutron and X-ray scattering indicate a strong interactio n between Al and transition metal atoms, which may be responsible for the high glass formability of these alloys. Furthermore, the results s how that the rare earth atoms play an important role in stabilizing th e amorphous structure in these alloys. Mechanical testing reveals that these Al-based metallic glasses have high tensile strengths up to app roximately 1300 MPa, approximately three times that of conventional al uminum alloys. Experimental results show that the tensile strength of these glassy alloys approaches the theoretical value. Thermal stabilit y studies suggest that the formation of these Al-based metallic glasse s is rather unusual, since they can readily be formed in the regions w here a eutectic region is absent. It was found that the glass formabil ity of these alloys is greatly enhanced by replacing a few percent of rare earth with a second transition metal element. As a result, sub-mi llimeter thick amorphous ribbons can be obtained at slow cooling rates . It may be possible to obtain bulk amorphous alloys by further optimi zing the composition. High tensile strengths combined with good glass formability make these Al glasses ideal candidates for high-strength l ow-density materials.