Lightweight, crash-sensitive automotive component

Abstract

The present invention provides a easting having increased crashworthiness including an aluminum alloy of about 6.0 wt % to about. 8.0 wt % Si; about 0.12 wt % to about 0.25 wt % Mg; less than or equal to about 0.35 wt % Cu; less than or equal to about 4.0 wt % Zn; less than or equal to about 0.6 wt % Mn; and less than or equal to about 0.15 wt % Fe, wherein the east body is treated to a T5 or T6 temper and has a tensile strength ranging from 100 MPa to 180 MPa and has a critical fracture strain greater than 10%. The present invention further provides a method of forming a casting having increased crashworthiness.

We claim: 
     
         1 . A method of casting an aluminum alloy into a crash-sensitive automotive component having a desired critical fracture strain for collision impact, the method comprising:
 selecting a crash-sensitive automotive component to cast;   providing a melt having an alloy comprising:
 about 6.0 wt % to about 7.8 wt % Si; 
 about 0.10 wt% to about 0.18 wt % Mg; 
 less than or equal to about 0.35 wt % Cu; 
 less than or equal to about 0.6 wt % Mn; 
 less than or equal to about 0.15 wt % Fe; 
 and, a balance of aluminum and impurities; 
   casting the melt into a cast body of the crash-sensitive automotive component; and,   heat treating the cast body, the treating including a solution heating at 450° C. to 550° C. for about ½ hour to about 6 hours, quenching, and aging at a temperature of about 150° C. to about 250° C. for about ½ hour to about 10 hours.   
     
     
         2 . The method of  claim 1 , wherein the heat treating comprises processing to a T6 temper. 
     
     
         3 . The method of  claim 1 , wherein the processing comprises a solution heat treatment of the crash-sensitive automotive component at 450° C. to 550° C. for a time period ranging from approximately a ½ hour to approximately 6 hours, quenching, and aging. 
     
     
         4 . The method of  claim 1 , wherein the Mn content is less than 0.15 wt %, and the casting of the cast body includes using a vacuum riserless casting/pressure riserless process. 
     
     
         5 . The method of  claim 1 , wherein the casting of the cast body includes using a sand core in combination with a vacuum riserless casting/pressure riserless process to provide a wall thickness as thin as 2.0 mm. 
     
     
         6 . The method of  claim 1 , wherein the cast body is in T6 temper and has a tensile yield strength ranging from 100 MPa to 180 MPa. 
     
     
         7 . The method of  claim 1 , wherein the Mn content of the cast body is less than about 0.05 wt % Mn. 
     
     
         8 . The method of  claim 1 . wherein the heat treating comprises T6 or T7 to further provide an elongation that exceeds 14%. 
     
     
         9 . The method of  claim 1 , the melt having about 7.0 wt % Si and from about 0.10 wt % to about 0.18 wt % Mg. 
     
     
         10 . The method of  claim 1 , the melt having about 0.12 wt % Mg and from about 6.0 wt % to about 7.8 wt % Si. 
     
     
         11 . A method of making a vehicle with a crash-sensitive automotive component having a desired performance during collision, the performance measured using critical fracture strain, the method comprising:
 obtaining a crash-sensitive automotive component that was produced using a process including:
 providing a melt having an alloy comprising:
 about 6.0 wt % to about 7.8 wt % Si: 
 about 0.10 wt % to about 0.18 wt % Mg; 
 less than or equal to about 0.35 wt % Cu; 
 less than or equal to about 0.6 wt % Mn; 
 less than or equal to about 0.15 wt % Fe; 
 and, a balance of aluminum and impurities; 
 
 casting the melt into a cast body of the crash-sensitive automotive component; and. 
 heat treating the cast body, the heat treating including a solution heating at 450° C. to 550° C. for about ½ hour to about 6 hours; quenching, and aging at a temperature of about 150° C. to about 250° C. for about ½ hour to about 10 hours; 
   and,   employing the crash-sensitive component in the vehicle.   
     
     
         12 . The method of  claim 11 , wherein the crash-sensitive automotive component is a part of a vehicle frame construction. 
     
     
         13 . The method of  claim 11 , wherein the crash-sensitive automotive component is a part of a body structure. 
     
     
         14 . The method of  claim 11 , wherein the crash-sensitive automotive component is selected from a group consisting of a bracket, a node, a crashbox, a crossmember, a subframe, and an engine cradle. 
     
     
         15 . The method of  claim 11 , wherein the heat treating comprises processing the cast body to a T6 temper. 
     
     
         16 . The method of  claim 11 , wherein the heat treating comprises a solution heat treatment of the cast body at 450° C. to 550° C. for a time period ranging from approximately a ½ hour to approximately 6 hours, quenching, and aging. 
     
     
         17 . An aluminum alloy casting having a desired critical fracture strain, the casting comprising:
 about 6.0 wt % to about 7.8 wt % Si;   about 0.10 wt % to about 0.18 wt % Mg;   less than or equal to about 0.35 wt % Cu;   less than or equal to about 0.6 wt % Mn;   less than or equal to about 0.15 wt % Fe,   and, a balance of aluminum and impurities;   
       the casting produced using a process that includes a solution heating at 450° C. to 550° C. for about ½ hour to about 6 hours, quenching, and aging at a temperature of about 150° C. to about 250° C. for about ½ hour to about 10 hours. 
     
     
         18 . The casting of  claim 17 , wherein the process includes heat treating to a T6 temper. 
     
     
         19 . The casting of  claim 17 , wherein the processing comprises a solution heat treatment of the crash-sensitive automotive component at 450° C. to 550° C. for a time period ranging from approximately a ½ hour to approximately 6 hours, quenching, and aging. 
     
     
         20 . The casting of  claim 17 , wherein the Mn content is less than 0.15 wt %, and the processing includes casting of the cast body using a vacuum riserless casting/pressure riserless process.