Aluminum alloy formulations for reduced hot tear susceptibility

Abstract

The present invention relates to modified alloy compositions for reduced hot tear susceptibility, the aluminum alloy comprising from 0.01 to 0.025% by weight of Sr; and TiB2, measured by its boron content, from 0.001 to 0.005% by weight of B. The invention also relates to a method of preventing or eliminating hot tears in an aluminum alloy comprising the step of combining with aluminum: from 0.01 to 0.025% by weight of Sr; and TiB2, measured by its boron content, from 0.001 to 0.005% by weight of B.

1 . An aluminum alloy comprising:
 i) From 0.010 to 0.025% by weight Sr; and   ii) TiB 2 , measured by its boron content, from 0.001 to 0.005% by weight B.   
   
   
       2 . The aluminum alloy according to  claim 1 , further comprising:
 i) 0.16% or less by weight excess Ti over the amount bound stoichiometrically with the B in TiB 2 .   
   
   
       3 . The aluminum alloy according to  claim 1 , selected from the group consisting of alloys comprising primarily aluminum and copper; alloys comprising primarily aluminum and manganese; alloys comprising primarily aluminum and silicon; alloys comprising primarily aluminum and magnesium; alloys comprising primarily aluminum, magnesium and silicon; and alloys comprising primarily aluminum, magnesium, zinc and copper. 
   
   
       4 . The aluminum alloy according to  claim 1 , comprising aluminum, magnesium, and silicon. 
   
   
       5 . The aluminum alloy according to  claim 4 , further comprising 0.010 to 0.020% by weight Sr, and TiB 2 , measured by its boron content, from 0.002 to 0.004% by weight B. 
   
   
       6 . The aluminum alloy according to  claim 1 , for shape casting. 
   
   
       7 . The aluminum alloy according to  claim 1 , for die casting. 
   
   
       8 . The aluminum alloy according to  claim 1 , wherein the alloy is an alloy cast prepared using a semi-solid casting process. 
   
   
       9 . The aluminum alloy according to  claim 1 , with a composition in weight percent of 0.6 to 0.8 Si, up to 0.12 Fe, 0.15 to 0.40 Cu, 0.8 to 1.2 Mg, 0.04 to 0.10 Cr, 0.006 to 0.025 Sr, 0.005 to 0.025% TiB 2 , measured by its boron content, from 0.001 to 0.005% by weight B, 0.16% or less of excess Ti over the amount bound stoichiometrically with the B in TiB 2 , incidental impurities each less than 0.05 and total less than 0.15, and balance with Al. 
   
   
       10 . The aluminum alloy according to  claim 9 , for casting by semi-solid processes. 
   
   
       11 . The aluminum alloy according to  claim 1 , with a composition in weight percent of 0.6 to 0.8 Si, up to 0.12 Fe, 0.15 to 0.40 Cu, 0.8 to 1.2 Mg, 0.04 to 0.10 Cr, 0.006 to 0.025 Sr, 0.005 to 0.025% TiB 2 , measured by its boron content, from 0.001 to 0.005% by weight B, 0.16% or less of excess Ti over the amount bound stoichiometrically with the B in TiB 2 , up to 0.45% by weight Mn, provided that the total Mn+Fe is between 0.55 to 0.65% by weight, incidental impurities each less than 0.05 and total less than 0.15, and balance Al. 
   
   
       12 . The aluminum alloy according to  claim 11 , for processing in the fully molten state. 
   
   
       13 . A method of preventing or eliminating hot tears in an aluminum alloy comprising the step of combining with aluminum:
 i) from 0.010 to 0.025% by weight Sr; and   ii) TiB 2 , measured by its boron content, from 0.001 to 0.005% by weight B.   
   
   
       14 . The method according to  claim 13 , further comprising the step of combining iii) 0.16% or less by weight excess Ti over the amount bound stoichiometrically with the B in TiB 2 . 
   
   
       15 . A shape cast part, cast from an alloy as defined in  claim 1 . 
   
   
       16 . The shape cast part according to  claim 15 , being a die cast. 
   
   
       17 . The shape cast part according to  claim 15 , cast from the alloy in a semi-solid state. 
   
   
       18 . A method of providing an aluminum alloy comprising combining with aluminum:
 i) from 0.010 to 0.025% by weight Sr; and   ii) TiB 2 , measured by its boron content, from 0.001 to 0.005% by weight B.   
   
   
       19 . The method according to  claim 18 , further comprising combining iii) 0.16% or less by weight excess Ti over the amount bound stoichiometrically with the B in TiB 2 . 
   
   
       20 . The method according to  claim 18 , wherein the alloy comprises primarily aluminum, magnesium, and silicon. 
   
   
       21 . The method according to  claim 18 , comprising casting the alloy. 
   
   
       22 . The method according to  claim 18 , comprising die casting the alloy. 
   
   
       23 . The method according to  claim 18 , comprising casting the alloy in a semi-solid state. 
   
   
       24 . The method according to  claim 18 , wherein the alloy is cooled from its liquidus state to its semi-solid state prior to casting. 
   
   
       25 . The method according to  claim 18 , wherein the alloy in its molten state may be maintained at temperature for a period of time sufficient to produce a semi-solid structure in the alloy. 
   
   
       26 . The method according to  claim 25 , wherein the period of time is from 1 second to about 2 minutes. 
   
   
       27 . The method according to  claim 23 , when the alloy is in its semi-solid state, said semi-solid state being globular solid phase dispersed in a liquid phase, prior to casting, at least some, but not all of the liquid phase is removed. 
   
   
       28 . The method for processing an aluminum alloy as defined in  claim 1 , having a liquidus temperature and a solidus temperature, the method comprising the steps of providing the alloy having a semi-solid range between the liquidus temperature and the solidus temperature of the alloy; heating the alloy to an alloy initial elevated temperature above the liquidus temperature to fully melt the alloy; reducing the temperature of the alloy from the initial metallic alloy elevated temperature to a semi-solid temperature of less than the liquidus temperature and more than the solidus temperature; maintaining the alloy at the semi-solid temperature for a sufficient time to produce a semi-solid structure in the alloy of a globular solid phase dispersed in a liquid phase, wherein the semi-solid structure has less than about 50 weight percent solid phase; removing at least some, but not all, of the liquid phase present in the semi-solid structure of the metallic alloy to form a solid-enriched semi-solid structure of the alloy, wherein the step of removing includes the step of removing liquid phase until the solid-enriched semi-solid structure has from about 35 to about 55 weight percent solid phase; and forming the alloy having the solid-enriched semi-solid structure into a shape.