Method of casting articles of a bulk-solidifying amorphous alloy

A method for casting an article of a bulk-solidifying amorphous metallic alloy, comprising the steps of:

• furnishing a casting mold defining the shape of the article;
• selecting a bulk-solidifying amorphous metallic alloy base composition which may be cooled from the melt at a cooling rate of less than about 500.degree. C. per second yet retain an amorphous metallic structure, and whose crystallization behavior during cooling is dependent upon its oxygen content;
• determining an operable oxygen content of the base composition for casting the base composition in the casting mold while retaining an amorphous state;
• preparing a casting charge of the base composition having an oxygen content of no greater than the operable oxygen content;
• heating the casting charge to a threshold temperature sufficiently greater than a crystallized melting temperature of the casting charge such that heterogeneous crystallization nucleation sites within the casting charge are eliminated;
• and thereafter
• casting the casting charge into the casting mold and permitting the casting charge of metal to cool and solidify at a rate of less than about 500.degree. C. per second such that the casting charge is amorphous.

A method for casting an article of a bulk-solidifying amorphous metallic alloy, comprising the steps of:

• furnishing a closed casting mold having a cavity therein defining the shape of the article;
• selecting a bulk-solidifying amorphous metallic alloy base composition which may be cooled from the melt at a cooling rate of less than about 500.degree. C. per second yet retain an amorphous metallic structure, and whose crystallization behavior during cooling is dependent upon its oxygen content;
• determining an operable oxygen content of the base composition for casting the base composition in the casting mold while retaining an amorphous state, wherein the step of determining an operable oxygen content includes the steps of
• obtaining a family of TTT crystallization curves of the bulk-solidifying amorphous metallic alloy for a range of oxygen contents,
• establishing a critical cooling curve experienced at a cooling location within the article during casting of the bulk-solidifying amorphous metallic alloy in the casting mold from the casting temperature, and
• selecting an operable oxygen content such that the critical cooling curve does not intersect the TTT crystallization curve for the selected oxygen content;
• preparing a casting charge of the base composition having an oxygen content of no greater than the operable oxygen content;
• heating the casting charge to a casting temperature greater than a crystallized melting temperature of the casting charge;
• and
• casting the casting charge into the casting mold and permitting the casting charge of metal to cool and solidify at a rate of less than about 500.degree. C. per second such that the casting charge is amorphous.