Molding and De-Molding of Metallic Glass Using Non-Disposable Molds

Abstract

A reusable mold comprising a flexible bulk metallic glass mold insert comprising one or more mold cavities removably coupled to a support mold and a method of making the reusable mold. The support mold is removable from the flexible bulk metallic glass mold insert without macroscopic elastic flexing or deforming of the support mold. The reusable mold may be used for molding one or more bulk metallic glass parts and the one or more molded bulk metallic glass parts may be released from the flexible bulk metallic glass mold insert by elastically flexing the flexible mold insert.

1 . A reusable mold comprising:
 a flexible bulk metallic glass mold insert comprising one or more mold cavities removably coupled to a support mold;   wherein the support mold is removable from the flexible hulk metallic glass mold insert without macroscopic deforming of the support mold.   
     
     
         2 . The reusable mold according to  claim 1 , wherein the mold insert is highly precise on the mold cavity side. 
     
     
         3 . The reusable mold according to  claim 1 , wherein the mold insert comprises a percent elasticity of at least 1.3%. 
     
     
         4 . The reusable mold according to  claim 1 , wherein the flexible bulk metallic glass mold insert comprises features on a miniature-length scale. 
     
     
         5 . The reusable mold according to  claim 1 , wherein the flexible bulk metallic glass mold insert comprises features having multiple length scales with at least one feature having a length scale on the miniature scale. 
     
     
         6 . The reusable mold according to  claim 1 , wherein the flexible bulk metallic glass mold insert is reusable multiple times. 
     
     
         7 . The reusable mold according to  claim 1 , wherein the flexible bulk metallic glass mold insert and the support mold comprise the same bulk metallic glass and are separated by a separation layer,
 wherein the separation layer prevents chemical bonding of the support layer and the bulk metallic glass mold insert.   
     
     
         8 . The reusable mold according to  claim 7 , wherein the separation layer deforms continuously with the bulk metallic glass mold insert and the support layer. 
     
     
         9 . The reusable mold according to  claim 7 , wherein the separation layer comprises a salt that is capable of providing a degree of wetting of the bulk metallic glass that is greater than 90 degrees. 
     
     
         10 . A method of making a reusable mold comprising one or more mold cavities, the method comprising the steps of:
 a) deforming a bulk metallic glass feedstock against a surface of a master mold to replicate a surface of the master mold and create a flexible bulk metallic glass mold insert comprising one or more mold cavities;   b) removably coupling the flexible bulk metallic glass insert to a support mold, and   c) removing the master mold from the flexible bulk metallic glass insert after the support mold has been removed from the insert mold;
 wherein the support mold is coupled to a surface of the flexible bulk metallic glass mold insert opposite the replicated surface; and 
 wherein the support mold is removable from the flexible bulk metallic glass mold insert without macroscopic elastic flexing or deforming of the support mold. 
   
     
     
         11 . A method of making a reusable mold according to  claim 10 , wherein the step of deforming the bulk metallic glass feed stock comprises deforming a sandwich comprising of a thin bulk metallic glass layer separated by a separation layer and a thick bulk metallic glass layer of the same type against the surface of the master mold to replicate the surface of the master mold;
 wherein the thin bulk metallic glass layer creates the flexible bulk metallic glass mold insert and the thick bulk metallic glass layer creates the support mold; and   wherein the thin bulk metallic glass layer faces the surface of the master mold.   
     
     
         12 . The method of making a reusable mold according to  claim 10 , wherein the flexible bulk metallic glass mold insert and the support mold comprise different bulk metallic glasses. 
     
     
         13 . The method of making a reusable mold according to  claim 10 , wherein a strength of the bulk metallic glass mold insert at the processing temperature of the bulk metallic glass of the support mold is at least one order of magnitude higher. 
     
     
         14 . The method according to  claim 10 , wherein the step of deforming the bulk metallic glass feed stock against the surface of the master mold comprises:
 a. increasing the temperature of the bulk metallic glass feed stock to a processing temperature, wherein the processing temperature is between the glass transition temperature and the crystallization temperature of the bulk metallic glass feed stock;   b. applying pressure to plastically deform the bulk metallic glass feed stock between a backing mold and the master mold and create the flexible bulk metallic glass mold insert; and   c. removing the backing mold from the flexible bulk metallic glass mold insert, wherein the backing mold is removed without any macroscopic flexing.   
     
     
         15 . The method according to  claim 10 , wherein the step of deforming the bulk metallic glass feed stock against the surface of the master mold comprises:
 a. increasing the temperature of the bulk metallic glass feed stock to a blow molding temperature, wherein the blow molding temperature is between the glass transition temperature and the crystallization temperature of the bulk metallic glass feed stock; and   b. blow molding the bulk metallic glass feed stock at the blow molding temperature and at low pressure to replicate the surface of the master mold and create the flexible bulk metallic glass mold insert;   c. deforming another BMG over the flexible bulk metallic glass insert, wherein the flexible bulk metallic glass insert covers the master mold.   
     
     
         16 . The method according to  claim 15 , wherein the blow molding pressure is less than 1 MPa. 
     
     
         17 . The method according to  claim 10 , wherein the step of deforming the bulk metallic glass feed stock against the surface of the master mold comprises:
 a. heating the bulk metallic glass feed stock into a super cooled liquid region of the bulk metallic glass feed stock; and   b. creating a favorable wetting behavior between the master mold and the bulk metallic glass feed stock to provide a reduction in surface energy and cause the bulk metallic glass feed stock to cover the surfaces of the one or more mold cavities.   
     
     
         18 . The method according to  claim 17 , wherein the wetting angle is between about 5 and about 90 degrees. 
     
     
         19 . The method according to  claim 18 , wherein the wetting angle is about 30 degrees. 
     
     
         20 . The method according to  claim 10 , wherein a Poisson's ratio of the flexible bulk metallic glass mold insert is at least 0.32. 
     
     
         21 . A method of molding a bulk metallic glass part using a reusable mold comprising a flexible bulk metallic glass mold insert removably coupled to a support mold, the flexible bulk metallic glass mold insert comprising one or more mold cavities, the method comprising the steps of:
 a. heating a bulk metallic glass to be molded into its supercooled liquid region;   b. disposing the bulk metallic glass into the one or more mold cavities in the flexible bulk metallic glass mold insert;   c. cooling the bulk metallic glass to solidify the bulk metallic glass within the one or more mold cavities and create the molded bulk metallic glass part;   d. removing the support mold from the flexible bulk metallic glass insert without macroscopic flexing of the support mold; and   e. releasing the one or more molded bulk metallic glass parts from the one or more mold cavities in the flexible bulk metallic glass mold insert by elastically flexing the flexible mold insert.   
     
     
         22 . The method according to  claim 21 , wherein the disposing step is carried out through an applied pressure. 
     
     
         23 . The method according to  claim 21 , wherein a plurality of cavities are filled in one molding operation and a change in thermal expansion difference, Au, between the flexible bulk metallic glass insert and the bulk metallic glass being molded is less than 10×10 −6 K −1 . 
     
     
         24 . The method according to  claim 21 , wherein a plurality of cavities are filled in one molding operation and the change in thermal expansion difference, Δα, between the flexible bulk metallic glass insert and the bulk metallic glass being molded is less than 5×10 −6  K −1 . 
     
     
         25 . The method according to  claim 21 , wherein the molded bulk metallic glass part comprises a complex geometry. 
     
     
         26 . The method according to  claim 25 , wherein the complex geometry comprises one or more undercuts. 
     
     
         27 . The method according to  claim 21 , wherein the support mold is removed from the flexible bulk metallic glass insert at a temperature that is at least 5% below the processing temperature of the molded bulk metallic glass part. 
     
     
         28 . The method according to  claim 21 , wherein the support mold is removed from the flexible bulk metallic glass insert at a temperature that is below the glass transition temperature of the molded bulk metallic glass part. 
     
     
         29 . The method according to  claim 28 , wherein the support mold is removed from the flexible bulk metallic glass insert at about room temperature. 
     
     
         30 . The method according to  claim 21 , wherein the strength of the flexible bulk metallic glass insert is at least 10 times that of the bulk metallic glass being molded at the processing temperature of the bulk metallic glass being molded. 
     
     
         31 . The method according to  claim 21 , wherein when the same bulk metallic glass is used for the bulk metallic glass mold insert and the support mold, the strength at forming temperature of the bulk metallic glass is at least one order of magnitude higher than that of the molded bulk metallic glass part. 
     
     
         32 . The method according to  claim 21 , wherein when different bulk metallic glasses are used for the bulk metallic glass mold insert and the support mold, the strength of the bulk metallic glass insert is at least one order of magnitude higher than that of the support mold during forming of the support mold. 
     
     
         33 . The method according to  claim 32 , Wherein the strength of the support mold is at least one order of magnitude higher than that of the molded bulk metallic glass part during forming of the molded bulk metallic glass part.