Al-Cu-Si-Ge alloys

Abstract

An Al—Cu—Si—Ge quaternary alloy uses Si—Ge additions to provide a reasonably dense and homogeneous distribution of precipitates. Heterogeneous nucleation on this Si—Ge template is used to enhance both strength and thermal stability. These precipitates are used as a template for heterogeneous precipitation of other hardening phases, particularly the •′ (Al 2 Cu) phase. Thus, a Si—Ge addition is used to provide a dense template of heterogeneous nucleation sites for subsequent precipitation of Al—Cu precipitates.

1 . A composition of matter, comprising a quaternary aluminum-copper-silicon-germanium alloy.  
     
     
         2 . The composition of  claim 1  wherein the alloy comprises aluminum-copper precipitates heterogeneously nucleated on silicon-germanium precipitates in an aluminum metal matrix.  
     
     
         3 . The composition of  claim 2  wherein the aluminum-copper precipitates are θ′ (Al 2 Cu) precipitates.  
     
     
         4 . The composition of  claim 1  having the general formula Al-xCu-ySi-zGe wherein x, y, z are the atomic percentages of the constituents.  
     
     
         5 . The composition of  claim 4  wherein y and z are each up to about 1 at. %, and x is up to about 3.5 at. %.  
     
     
         6 . The composition of  claim 5  wherein y and z are each up to about 0.5 at. %.  
     
     
         7 . The composition of  claim 4  wherein the alloy comprises aluminum-copper precipitates heterogeneously nucleated on silicon-germanium precipitates in an aluminum metal matrix.  
     
     
         8 . The composition of  claim 7  wherein the aluminum-copper precipitates are θ′ (Al 2 Cu) precipitates.  
     
     
         9 . The composition of  claim 5  wherein the alloy comprises aluminum-copper precipitates heterogeneously nucleated on silicon-germanium precipitates in an aluminum metal matrix.  
     
     
         10 . The composition of  claim 9  wherein the aluminum-copper precipitates are θ′ (Al 2 Cu) precipitates.  
     
     
         11 . A method of forming a precipitate hardened aluminum alloy, comprising melting aluminum, copper, silicon, and germanium together to first form silicon-germanium precipitates which serve as nucleation sites, and then form aluminum-copper precipitates on the silicon-germanium nucleation sites.  
     
     
         12 . The method of  claim 11  wherein the atomic percentage of Cu is greater than zero and ranges up to about 3.5%, and the atomic percentages of Si and Ge are each greater than zero and each range up to about 1%.  
     
     
         13 . The method of  claim 12  wherein the atomic percentages of Si and Ge are each up to about 0.5%.  
     
     
         14 . The method of  claim 11  further comprising annealing the alloy.  
     
     
         15 . The method of  claim 11  comprising annealing at about 500° C. for about 24 hours.  
     
     
         16 . The method of  claim 14  further comprising aging the annealed alloy.  
     
     
         17 . The method of  claim 16  comprising aging at about 190° C. for about 1-3 hours.  
     
     
         18 . A precipitate hardened aluminum alloy formed by the method of  claim 11 .  
     
     
         19 . A precipitate hardened aluminum alloy formed by the method of  claim 12 .  
     
     
         20 . A precipitate hardened aluminum alloy formed by the method of claim  17 .