High-strength aluminum casting alloys resistant to hot tearing

Abstract

An aluminum casting alloy resistant to hot tearing includes, in wt %, about 4.0 to about 6.9 Zn, about 2.0 to about 3.5 Mg, about 0.6 to about 1.2 Cu, about 0.38 to about 0.57 Sc, about 0.18 to about 0.28 Zr, and the balance Al and impurities, substantially excluding Fe, Mn, and Si, said alloy characterized by a freezing range of less than about 150° C., solidus temperature above about 490° C., and eutectic phase fraction above about 5% at the late stages of solidification. The alloy is processed to form a dispersion of L1 2 particles inoculating fcc grains with a grain diameter of about 40 to about 60 μm, and η′-phase precipitates enabling an ambient yield strength from about 410 MPa to about 540 MPa.

1 . An aluminum casting alloy with anti tear characteristics comprising, in wt %, about 4.0 to about 6.9 Zn, about 2.0 to about 3.5 Mg, about 0.6 to about 1.2 Cu, about 0.38 to about 0.57 Sc, about 0.18 to about 0.28 Zr, and the balance Al and impurities, substantially excluding Fe, Mn, and Si, said alloy characterized by a dispersion of L1 2  particles inoculating fcc grains, and η′-phase precipitates. 
     
     
         2 . The alloy of  claim 1  wherein the mean grain diameter of the fcc grains is about 40 to 60 μm. 
     
     
         3 . The alloy of  claim 1  wherein the η′-phase precipitates have a mean radius of less than about 5 nm. 
     
     
         4 . The alloy of  claim 1  having less than about 0.0075 weight percent Fe, less than about 0.2 weight percent Mn and less than about 0.03 weight percent Si. 
     
     
         5 . The alloy of  claim 1  having the following constituents in weight percent: about 5.8-6.8 Zn, 2.9-3.5 Mg, 1.0-1.2 Cu, 0.52 Sc, and 0.20 Zr. 
     
     
         6 . The alloy of  claim 1  having the following constituents in weight percent: about 4.8-5.8 Zn, 2.7-3.3 Mg, 1.0-1.2 Cu, 0.55 Sc, and 0.25 Zr. 
     
     
         7 . The alloy of  claim 1  having the following constituents in weight percent: about 4.0-5.0 Zn, 2.0-2.6 Mg, 0.52-0.72 Cu, 0.42 Sc and 0.25 Zr. 
     
     
         8 . An aluminum casting alloy with anti tear characteristics comprising, in wt %, about 4.0 to about 6.9 Zn, about 2.0 to about 3.5 Mg, about 0.6 to about 1.2 Cu, about 0.38 to about 0.57 Sc, about 0.18 to about 0.28 Zr, and the balance Al and impurities, substantially excluding Fe, Mn, and Si, said alloy characterized by a freezing range of less than about 150° C., solidus temperature above about 490° C., and eutectic phase fraction above about 5% at the late stages of solidification. 
     
     
         9 . An aluminum casting alloy with anti tear characteristics comprising, in wt %, about 4.0 to about 6.9 Zn, about 2.0 to about 3.5 Mg, about 0.6 to about 1.2 Cu, about 0.38 to about 0.57 Sc, about 0.18 to about 0.28 Zr, and the balance Al and impurities, substantially excluding Fe, Mn, and Si, said alloy characterized by a freezing range of less than about 150° C., solidus temperature above about 490° C., and eutectic phase fraction above about 5% at the late stages of solidification and a dispersion of L1 2  particles inoculating fcc grains, and η′-phase precipitates. 
     
     
         10 . An aluminum casting alloy with anti tear characteristics comprising, in wt %, about 4.0 to about 6.9 Zn, about 2.0 to about 3.5 Mg, about 0.6 to about 1.2 Cu, about 0.38 to about 0.57 Sc, about 0.18 to about 0.28 Zr, and the balance Al and impurities, substantially excluding Fe, Mn, and Si, said alloy characterized by a freezing range of less than about 150° C., solidus temperature above about 490° C., and eutectic phase fraction above about 5% at the late stages of solidification, a dispersion of L1 2  particles inoculating fcc grains with a grain diameter of about 40 to about 60 μm, and η′-phase precipitates, and ambient yield strength from about 410 MPa to about 540 MPa.