Synthesis and Properties of Aluminum-Based Metallic Glasses Containing RareEarths

摘要

A new family of metallic glasses containing up to 92 at. %of aluminum has beensynthesized in Al-TM-RE (where TM=transition metals, RE=yttrium and rare earths) alloy systems using a melt-spinning technique. The atomic structure, mechanical properties, thermal and mechanical stability of these metallic glasses have been studied. Structural studies by pulsed neutron and X-ray scattering indicate a strong interaction between Al and transition metal atoms, which may be responsible for the high glass formability of these alloys. Furthermore, the results show that the rare earth atoms play an important role in stabilizing the amorphous structure in these alloys. Mechanical testing reveals that these Al-based metallic glasses have high tensile strengths up to approx. 1300 MPa, approximately three times that of conventional aluminum alloys. Experimental results show that the tensile strength of these glassy alloys approaches the theoretical value. Thermal stability studies suggest that the formation of these Al-based metallic glasses is rather unusual, since they can readily be formed in the regions where a eutectic region is absent. It was found that the glass formability of these alloys is greatly enhanced by replacing a few percent of rare earth with a second transition metal element. As a result, sub-millimeter thick amorphous ribbons can be obtained at slow cooling rates. It may be possible to obtain bulk amorphous alloys by further optimizing the composition. High tensile strengths combined with good glass formability make these Al glasses ideal candidates for high-strength low-density materials. jg.