Method for producing foamed aluminum products

Abstract

The present invention is directed to a method for making porous aluminum product and products therefrom and, in particular, a method of rapidly solidifying a liquid metal foam produced by the incorporation of gas forming agents into an aluminum melt. The aluminum melt may be stabilized to support the creation of liquid metal foam by the addition of metal and/or ceramic additives. The decomposition of the gas forming agents and subsequent expansion of the gaseous products is controlled through the use of a reactor, wherein temperature, pressure and transit time can be adjusted to match the decomposition kinetics of the gas forming agent. The invention allows for the economical production of liquid metal foam of uniform cell size that can be continuously cast into sheet, plate and profile sections. Such metal foam products may be used in structural, thermal and acoustic applications.

What is claimed is:  
     
         1 . A method of making a porous aluminum alloy product comprising the steps of: 
 a. providing an incoming flow of an aluminum alloy melt;    b. incorporating small, stable solid particles into said aluminum alloy to increase the melt viscosity and to service as gas bubble nucleation and anchor sites c. incorporating gas forming agents into said aluminum alloy melt to form an inoculated aluminum alloy melt;    c. transferring said inoculated aluminum alloy melt into reactor vessel;    d. maintaining said inoculated aluminum alloy melt in said reactor vessel under conditions of pressure, temperature and time so as to initiate decomposition of the foaming agent;    e. releasing said inoculated aluminum alloy melt from said reactor vessel so as to allow expansion of the gas, thereby creating a liquid metal foam;    f. rapidly solidifying said liquid metal foam to create a solid foam.    
     
     
         2 . The method according to  claim 1  wherein metal and/or ceramic additions are added to said aluminum alloy melt to provide stabilization of the liquid metal foam.  
     
     
         3 . The method according to  claim 2  wherein said additions are added prior to incorporating said gas-forming agents.  
     
     
         4 . The method according to  claim 2  wherein said additions are added mixed with said gas forming agents prior to step b.  
     
     
         5 . The method according to  claim 2  wherein said additions are added after step b.  
     
     
         6 . The method according to  claim 1  wherein said liquid metal foam is rapidly solidified to create a continuously cast shaped profile product.  
     
     
         7 . The method according to  claim 1  wherein said liquid metal foam is rapidly solidified to create a continuously cast sheet or plate product.  
     
     
         8 . The method according to  claim 1  wherein said liquid metal foam is solidified between moving twin belts.  
     
     
         9 . The method according to  claim 1  wherein said liquid metal foam is solidified between moving twin rolls.  
     
     
         10 . The method according to  claim 1  wherein said liquid metal foam is solidified onto a single roll.  
     
     
         11 . The method according to  claim 1  wherein a sheet of another aluminum alloy is laminated to one or both sides of the foam sheet by feeding sheet to the caster and simultaneously casting the foam and laminating the additional sheet or sheets thereto.  
     
     
         12 . A method according to  claim 2  wherein said metal and/or ceramic additions are reactive to said aluminum melt such that the additions are wetted by the alloy melt.  
     
     
         13 . A method according to  claim 2  wherein said metal and/or ceramic additions are treated to form a reactive coating such that the additions are wetted by the alloy melt.  
     
     
         14 . The method according to  claim 13  wherein the metal and/or ceramic additions include a reactive coating such as a nitride, borate, nitrate, phosphate, sulfate, amine or reactive metal such as iron, nickel, copper or silicon.  
     
     
         15 . The method according to  claim 1  wherein said nitride is Mg 3 N 2 .  
     
     
         16 . The method according to  claim 2  wherein the metal and/or ceramic additions are the highly oxidized by-products of the aluminum melting and recycling path.  
     
     
         17 . The method according to  claim 1  wherein said transferring is accomplished by gravity feed.  
     
     
         18 . The method according to  claim 1  wherein said transferring is accomplished by means of a pump.  
     
     
         19 . The method according to  claim 13  wherein the metal and/or ceramic additions include a reactive coating such alkali metal, alkaline earth, and transition metal oxides, sulfides and halides.