Method for the manufacture of metal foams by electrolytic reduction of porous oxidic preforms

Abstract

A method for the manufacture of a foamed metal or alloy article including the steps of: A) selecting a particulate feedstock having suitable proportions of a metal element or combination of metal elements M 1 contaminated by one or more contaminants X to form an alloy suitable for the foamed article; B) mixing the feedstock with a binder to form a slurry; C) preforming the slurry into a near net shape of the desired article and drying the preform to remove the binder; D) sintering the dried preform to provide a bonded foamed article; E) introducing the sintered article into an electrochemical cell, the cell containing a liquid electrolyte comprising a fused salt or mixture of salts generally designated as M 2 Y in which contaminant(s) X is soluble, and a relatively inert anode; F) conducting electrolysis under conditions favourable to the selective dissolution of the contaminant(s) X in preference to the M 2 cation; and G) following electrolysis reclaiming the purified foam article from the cathode.

1 . A method for the manufacture of a metal or alloy mass from a metal oxide or mixed metal oxide feedstock, by electrolysis in a fused salt of M 2 Y or a mixture of such salts under conditions such that ionisation of oxygen rather than M 2  deposition occurs and that oxygen dissolves in the electrolyte M 2 Y, characterised in that the feedstock consists of a foamed, dried and sintered metal oxide preform and produces a foamed metal or alloy mass.  
     
     
         2 . A method according to  claim 1  wherein the preform is foamed by passing a gas through a slurry comprising a metal oxide particulate, binder and water.  
     
     
         3 . A method according to  claim 1  wherein the preform is foamed by gas evolved from a chemical reaction of organic foaming agents and the foam is then fired to remove the organic material.  
     
     
         4 . A method according to  claim 1  wherein the preform is made by infiltrating a natural or synthetic polymeric foam with a slurry comprising a metal oxide particulate, binder and water and subsequently burning off the polymeric foam.  
     
     
         5 . A method according to  claim 4  wherein the vaporisation point of the foam template is lower than the melting point of the metal oxide or mixed metal oxide to be foamed.  
     
     
         6 . A method according to any preceding claim wherein the preform is in the near net shape of the intended metal or alloy article.  
     
     
         7 . A method as claimed in any preceding claim wherein the metal oxide comprises TiO 2 .  
     
     
         8 . A method as claimed in any preceding claim wherein Y is chloride.  
     
     
         9 . A method as claimed in any preceding claim wherein M 2  is calcium.  
     
     
         10 . A method as claimed in any preceding claim wherein the alloy is a beta titanium alloy.  
     
     
         11 . A method as claimed in any preceding claim further comprising applying a metal working process to the metal or alloy mass after it has been reclaimed.  
     
     
         12 . Armour manufactured according to the method of any of  claims 1  to  11 .  
     
     
         13 . Armour as claimed in  claim 12  wherein the alloy is Ti-6Al-4V alloy.  
     
     
         14 . An orthopaedic implant for a human or animal body manufactured according to the method of any of  claims 1  to  11 .  
     
     
         15 . An orthopaedic implant according to  claim 14  wherein said implant comprises a fully dense core and an outer foam layer.