Magnesium-zirconium alloying

Abstract

Zirconium sponge can be chemically depassivated by treatment with hydrofluoric acid to improve the ability of molten magnesium/magnesium alloy to dissolve zirconium from the treated zirconium sponge and to form a melt containing substantially evenly distributed particles of zirconium. Optical micrographs showing the grain refining ability of pretreated sponge when added to pure magnesium at 680° C. All micrographs are of the same magnification. (a) Pure magnesium, (b) after adding 1 wt % sponge followed by 20 minutes manual stirring, and (c) after a further 10 minutes stirring.

1 . A method for treating zirconium metal, the method comprising chemically depassivating the zirconium metal.  
     
     
         2 . A method for treating zirconium sponge, the method comprising chemically depassivating the zirconium sponge to form treated zirconium sponge.  
     
     
         3 . A method as claimed in  claim 2  wherein the zirconium sponge is chemically depassivated by treatment with a source of fluoride ions.  
     
     
         4 . A method as claimed in  claim 3  wherein the source of fluoride ions is an acidified solution containing fluoride ions.  
     
     
         5 . A method as claimed in  claim 3  wherein the source of fluoride ions is hydrofluoric acid.  
     
     
         6 . A method for treating zirconium sponge, the method comprising treating the zirconium sponge with a solution containing fluoride ions to form treated zirconium sponge.  
     
     
         7 . Treated zirconium sponge prepared by a method as claimed in  claim 2 .  
     
     
         8 . Zirconium sponge compromising an agglomerate of zirconium particles and having a surface layer containing fluorine containing compounds at least partially coating at least some of the particles.  
     
     
         9 . Zirconium sponge as claimed in  claim 8  wherein fluorine containing compounds are zirconium fluoride compounds.  
     
     
         10 . Zirconium sponge as claimed in  claim 9  wherein the zirconium fluoride compounds have the formula Zr x F y .nH 2 O.  
     
     
         11 . A method of manufacturing a magnesium-zirconium master alloy, the method comprising the steps of: 
 (a) mixing treated zirconium sponge as claimed in  claim 7  with molten magnesium/magnesium alloy to form a magnesium-zirconium melt containing dissolved zirconium and zirconium particles; and    (b) casting the magnesium-zirconium melt to solidify as the magnesium-zirconium master alloy.    
     
     
         12 . A magnesium-zirconium master alloy manufactured by a method as claimed in  claim 11 .  
     
     
         13 . A magnesium-zirconium master alloy as claimed in  claim 12  containing 10-50% by weight zirconium.  
     
     
         14 . A magnesium-zirconium master alloy as claimed in  claim 12  containing 20-40% by weight zirconium.  
     
     
         15 . A magnesium-zirconium master alloy as claimed in  claim 12 , wherein 90% of the zirconium particles are sized less than 5 μm.  
     
     
         16 . A magnesium-zirconium master alloy containing dissolved zirconium and zirconium particles in the substantial absence of halide inclusions, wherein 90% of the zirconium particles are sized less than 5 μm.  
     
     
         17 . A magnesium-zirconium master alloy as claimed in  claim 15  wherein 90% of the zirconium particles are sized less than 3 μm.  
     
     
         18 . A method of adding zirconium as an alloying element to molten magnesium/magnesium alloy, the method comprising mixing treated zirconium sponge as claimed in  claim 7  with the molten magnesium/magnesium alloy.  
     
     
         19 . A method of adding zirconium as an alloying element to molten magnesium/magnesium alloy, the method comprising mixing a magnesium-zirconium master alloy as claimed in  claim 12  with the molten magnesium/magnesium alloy.  
     
     
         20 . A magnesium alloy containing zirconium prepared by a method as claimed in  claim 18.