High strength reduced be casting alloy

Abstract

The Be content of Be Al alloys suitable for investment casting, which contain a small but suitable amount of Ag, can be significantly reduced without adversely affecting their thermal or investment casting properties by including significantly more Si in the alloy than done in the past.

1 . A Be Al alloy suitable for investment casting purposes, the alloy comprising about 40 to 55 wt. % Be, about 1.3 to 7.0 wt. % Ag, about 1.5-7 wt. % Si, about 0.5-6.0 wt. % of Ni, Co, Cu or mixtures thereof, and no more than about 3 wt. % optional ingredients, with the balance being Al plus incidental impurities, wherein the Be/Al ratio of the alloy is <˜2.0, the combined amounts of Si and Ag in the alloy is >4 wt. %, the combined amounts of Si, Ag, Ni, Co and Cu in the alloy is ≧˜6 wt. %, and further wherein the alloy has a coefficient of thermal expansion of ≦15 μm/m (ppm), a 0.2% yield strength of ≧200 MPa and an ultimate tensile strength of ≧250 MPa. 
     
     
         2 . The alloy of  claim 1 , wherein the Be/Al ratio is ≦˜1.6. 
     
     
         3 . The alloy of  claim 2 , wherein the Be/Al ratio is ≦˜1.4. 
     
     
         4 . The alloy of  claim 1 , wherein the combined amounts of Ag and Si in the alloy is ≧˜5.0 wt. % 
     
     
         5 . The alloy of  claim 4 , wherein the combined amounts of Ag and Si in the alloy is ≧˜5.8 wt. %. 
     
     
         6 . The alloy of  claim 1 , wherein the combined amounts of Si, Ag, Ni, Co and Cu in the alloy is ≧˜7.0 wt. %. 
     
     
         7 . The alloy of  claim 6 , wherein the combined amounts of Si, Ag, Ni, Co and Cu in the alloy is ≧˜8.0 wt. %. 
     
     
         8 . The alloy of  claim 1 , wherein the alloy has a 0.2% yield strength of ≧220 MPa and an ultimate tensile strength of ≧265 MPa. 
     
     
         9 . The alloy of  claim 8 , wherein the alloy has a 0.2% yield strength of ≧230 MPa and an ultimate tensile strength of ≧280 MPa. 
     
     
         10 . The alloy of  claim 1 , wherein the alloy contains about 45 to 55 wt. % Be, about 2.0-7.0 wt. % Si, about 1.5 to 6.0 wt. % Ag, and no more than about 1.5 wt. % optional ingredients, about 1-5 wt. % of Ni, Co, Cu or mixtures thereof, with the balance being Al plus incidental impurities, wherein the Be/Al ratio is ≦˜1.6., the combined amounts of Si and Ag is ≧˜5.0 wt. %, the combined amounts of Si, Ag, Ni, Co and Cu in the alloy is ≧˜7 wt. %, and further wherein the alloy has a 0.2% yield strength of ≧220 MPa and an ultimate tensile strength of ≧265 MPa. 
     
     
         11 . The alloy of  claim 10 , wherein the alloy contains ˜47.5 to <˜50 wt. % Be, about 2.5-6.0 wt. % Si, about 2-5 wt. % Ag, about 2-4 wt. % of Ni, Co, Cu or mixtures thereof, and no more than about 0.5 wt. % optional ingredients, with the balance being Al plus incidental impurities, wherein the combined amounts of Si and Ag is ≧˜5.8 wt. %, the combined amounts of Si, Ag, Ni, Co and Cu in the alloy is ≧˜8 wt. %, and further wherein the alloy has a 0.2% yield strength of ≧230 MPa and an ultimate tensile strength of ≧280 MPa. 
     
     
         12 . The alloy of  claim 1 , wherein the alloy contains about 0.01 to 0.1 wt. % strontium, sodium, calcium, antimony or mixtures thereof. 
     
     
         13 . The alloy of  claim 1 , wherein the alloy contains about 0.02 to 0.06 wt. % strontium. 
     
     
         14 . The alloy of  claim 1 , wherein the alloy contains less than about 50 wt. % Be.