Trace element modification of iron-rich phase in aluminum-silicon alloys to accommodate high iron content

Abstract

Methods and heat-treated cast aluminum alloy components for a vehicle formed from an aluminum alloy having high levels of recycled aluminum scrap are provided. The alloy may have, by mass, silicon at ≥5% to ≤11%, magnesium at ≤0.5%, iron at ≥0.2% to ≤1.1%, copper at ≤0.5%, zinc at ≤0.5%, titanium at ≤0.2%, chromium at ≤0.02%, manganese at ≤0.05%, strontium at ≤200 ppm; an alloying element at ≥50 ppm to ≤500 ppm selected from the group consisting of: barium, lanthanum, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and combinations thereof, and a balance aluminum. The heat-treated cast aluminum alloy component is substantially free of faceted iron-containing intermetallics having a platelet shape and at least one region has a yield strength of ≥180 MPa and an elongation of ≥7%.

What is claimed is: 
     
         1 . A heat-treated cast aluminum alloy component for a vehicle formed from an aluminum alloy comprising:
 silicon (Si) at greater than or equal to about 5% to less than or equal to about 11% by mass;   magnesium (Mg) at less than or equal to about 0.5% by mass;   iron (Fe) at greater than or equal to about 0.2% to less than or equal to about 1.1% by mass;   copper (Cu) at less than or equal to about 0.5% by mass;   zinc (Zn) at less than or equal to about 0.5% by mass;   titanium (Ti) at less than or equal to about 0.2% by mass;   chromium (Cr) at less than or equal to about 0.02% by mass;   manganese (Mn) at less than or equal to about 0.05% by mass;   strontium (Sr) at less than or equal to about 200 ppm;   an alloying element at greater than or equal to about 50 ppm to less than or equal to about 500 ppm, wherein the alloying element is selected from the group consisting of: barium (Ba), lanthanum (La), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and combinations thereof; and   a balance aluminum (Al), wherein the heat-treated cast aluminum alloy component is substantially free of faceted iron-containing intermetallics having a platelet shape and at least one region has a yield strength of greater than or equal to about 180 MPa and an elongation of greater than or equal to about 7%.   
     
     
         2 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the aluminum alloy comprises iron (Fe) at greater than or equal to about 0.25% by mass. 
     
     
         3 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the aluminum alloy comprises iron (Fe) at greater than or equal to about 0.4% by mass. 
     
     
         4 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the aluminum alloy comprises:
 silicon (Si) at greater than or equal to about 6.5% to less than or equal to about 8% by mass;   magnesium (Mg) at greater than or equal to about 0.3% to less than or equal to about 0.4% by mass;   iron (Fe) at greater than or equal to about 0.2% to less than or equal to about by mass;   copper (Cu) at less than or equal to about 0.1% by mass;   zinc (Zn) at less than or equal to about 0.1% by mass; and   the alloying element at greater than or equal to about 50 ppm to less than or equal to about 300 ppm.   
     
     
         5 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the aluminum alloy comprises:
 silicon (Si) at greater than or equal to about 6.5% to less than or equal to about 8% by mass;   magnesium (Mg) at greater than or equal to about 0.3% to less than or equal to about 0.4% by mass;   iron (Fe) at greater than or equal to about 0.4% to less than or equal to about by mass;   copper (Cu) at less than or equal to about 0.1% by mass;   zinc (Zn) at less than or equal to about 0.1% by mass; and   the alloying element at greater than or equal to about 50 ppm to less than or equal to about 300 ppm.   
     
     
         6 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the heat-treated cast aluminum alloy component comprises an iron-containing intermetallic that has a non-faceted rounded morphology. 
     
     
         7 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the heat-treated cast aluminum alloy component comprises an iron-containing intermetallic comprising iron (Fe), silicon (Si), and aluminum (Al) and after heat treatment, the iron-containing intermetallic is spheroidized and has an average equivalent diameter of greater than or equal to about 1 micrometer to less than or equal to about 5 micrometers. 
     
     
         8 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the alloying element is selected from the group consisting of: barium (Ba), samarium (Sm), europium (Eu), erbium (Er), and combinations thereof. 
     
     
         9 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the yield strength is greater than or equal to about 210 MPa. 
     
     
         10 . The heat-treated cast aluminum alloy component of  claim 1 , wherein the heat-treated cast aluminum alloy component is an automotive component. 
     
     
         11 . The heat-treated cast aluminum alloy component of  claim 10 , wherein the automotive component is selected from the group consisting of: an internal combustion engine component, a valve, a piston, a turbocharger component, a rim, a wheel, a subframe, a knuckle, a control arm, a ring and combinations thereof. 
     
     
         12 . A method of making a recycled aluminum alloy component comprising:
 melting an aluminum alloy precursor comprising greater than or equal to about 70% by mass aluminum recycling scrap to form a molten alloy, the aluminum alloy precursor having a composition comprising:
 silicon (Si) at greater than or equal to about 5% to less than or equal to about 11% by mass; 
 magnesium (Mg) at less than or equal to about 0.5% by mass; 
 iron (Fe) at greater than or equal to about 0.2% to less than or equal to about 1.1% by mass; 
 copper (Cu) at less than or equal to about 0.5% by mass; 
 zinc (Zn) at less than or equal to about 0.5% by mass; 
 titanium (Ti) at less than or equal to about 0.2% by mass; 
 chromium (Cr) at less than or equal to about 0.02% by mass; 
 manganese (Mn) at less than or equal to about 0.05% by mass; 
 strontium (Sr) at less than or equal to about 200 ppm; and 
 a balance aluminum (Al); 
   introducing a master alloy into the molten alloy, the master alloy comprising a matrix element selected from the group consisting of: aluminum (Al), magnesium (Mg), silicon (Si), and combinations thereof and an alloying element selected from the group consisting of: barium (Ba), lanthanum (La), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and combinations thereof; and   casting by solidifying the molten alloy at a maximum rate of cooling of less than or equal to about 20° C./second to form an as-cast recycled aluminum alloy component; and   heat treating the as-cast recycled aluminum alloy component to be substantially free of faceted iron-containing intermetallics having a platelet shape and to have at least one region having a yield strength of greater than or equal to about 180 MPa and an elongation of greater than or equal to about 7%.   
     
     
         13 . The method of  claim 12 , wherein the alloying element is present in the master alloy at greater than or equal to about 5% to less than or equal to about 30% by mass. 
     
     
         14 . The method of  claim 12 , wherein the master alloy is added at greater than or equal to about 0.01% to less than or equal to about 2.5% by mass to the molten alloy. 
     
     
         15 . The method of  claim 12 , further comprising: (i) melt refining of the molten alloy and degassing prior to the introducing the master alloy; (ii) melt refining of the molten alloy and degassing after the introducing the master alloy and prior to the casting; or both (i) and (ii). 
     
     
         16 . The method of  claim 12 , wherein the heat treating comprises tempering the as-cast recycled aluminum alloy component at a temperature of greater than or equal to about 500° C. to less than or equal to about 550° C. for greater than or equal to about 1 hour to less than or equal to about 10 hours. 
     
     
         17 . The method of  claim 12 , wherein the heat treating comprises ageing the as-cast recycled aluminum alloy component at a temperature of greater than or equal to about 130° C. to less than or equal to about 190° C. for greater than or equal to about 1 hour to less than or equal to about 10 hours. 
     
     
         18 . The method of  claim 12 , further comprising quenching after the heat treating with water at a temperature in the range of greater than or equal to about 30° C. to less than or equal to about 100° C. 
     
     
         19 . The method of  claim 12 , wherein the heat treating comprises tempering the as-cast recycled aluminum alloy component at a temperature of greater than or equal to about 530° C. to less than or equal to about 550° C. for greater than or equal to about 1 hour to less than or equal to about 10 hours, followed by quenching after the heat treating with water at a temperature in the range of greater than or equal to about to less than or equal to about 100° C., and then ageing the recycled aluminum alloy component at a temperature of greater than or equal to about 130° C. to less than or equal to about 190° C. for greater than or equal to about 1 hour to less than or equal to about 10 hours. 
     
     
         20 . The method of  claim 12 , wherein the yield strength is greater than or equal to about 210 MPa.