Melt overheating method for improved toughness and glass-forming ability of metallic glasses

Abstract

A method of forming a bulk metallic glass is provided. The method includes overheating the alloy melt to a temperature above a threshold temperature, Ttough, associated with the metallic glass demonstrating substantial improvement in toughness compared to the toughness demonstrated in the absence of overheating the melt above Tliquidus, and another threshold temperature, TGFA, associated with the metallic glass demonstrating substantial improvement in glass-forming ability compared to the glass-forming ability demonstrated in the absence of overheating the melt above Tliquidus. After overheating the alloy melt to above Ttough and TGFA, the melt may be cooled and equilibrated to an intermediate temperature below both Ttough and TGFA but above Tliquidus, and subsequently quenched at a high enough rate to form a bulk metallic glass.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application claims the benefit of U.S. Provisional Patent Application No. 61 / 755,177, entitled “Melt Overheating Method For Improved Toughness and Glass-Forming Ability of Metallic Glasses” filed on Jan. 22, 2013, which is incorporated herein by reference in its entirety.FIELD[0002]The present disclosure is directed to a method of overheating the melt of an alloy capable of forming metallic glass prior to quenching the melt in order to improve the glass-forming ability of the alloy and / or the toughness of the metallic glass.BACKGROUND[0003]Overheating the melt of alloys capable of forming metallic glass to temperatures sufficiently higher than the melting temperature is shown to influence certain kinetic properties of the liquid. Specifically, Lin et al. (U.S. Pat. No. 5,797,443) demonstrated that by overheating the melt of a bulk-solidifying Zr-based amorphous metal above a threshold temperature, which is sufficiently higher ...

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Benefits of technology

[0008]In another embodiment, the temperature of the overheated alloy melt is also above another threshold temperature, TGFA, associated with the alloy demonstrating increased glass-forming ability compared to the glass-forming ability demonstrated by heating the alloy melt just above Tliquidus.

[0014]In yet another embodiment, the metallic glass article having a lateral dimension of at least 0.5 mm made according to the present method is capable of undergoing macroscopic plastic deformation without fracturing catastrophically under a bending load.

Problems solved by technology

Lin et al. conjectured that by overheating the melt, certain oxide inclusions were dissolved into the melt and therefore could not serve as sites for heterogeneous nucleation of crystalline phases.

However, Lin et al. did not demonstrate, suggest, or imply that overheating the melt above some threshold temperature would have any influence on the mechanical properties of the amorphous metal, such as the fracture toughness.

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