High pressure die cast (hpdc) aluminum alloy heat treatment for improved rivetability via modification of as-cast structure

Abstract

A method of treating a high pressure die cast (HPDC) material to improve rivetability is provided. The method includes exposing the HPDC material to a temperature between 300° C. and 450° C. for a time period between 10 minutes and 5 hours in a heat treatment step. In this method, the heat treatment results in eutectic silicon spheroidization of the HPDC material such that the HPDC material does not crack after rivet installation. The method further includes the step of exposing the HPDC material to a subsequent heat treatment step at about 180° C. for about 30 minutes after quenching. Moreover, the quenching may be a forced air quench for a period of 6° C./s.

What is claimed is: 
     
         1 . A method of treating a high pressure die cast (HPDC) material to improve rivetability, the method comprising:
 exposing the HPDC material to a temperature between 300° C. and 450° C. for a time period between 10 minutes and 5 hours in a heat treatment step;   wherein the heat treatment result in eutectic silicon spheroidization of the HPDC material such that the HPDC material does not crack due to rivet installation,   wherein the composition of the HPDC material comprises:   
       
         
           
                 
                 
                 
                 
               
                     
                     
                 
                     
                     
                   Minimum 
                   Maximum 
                 
                     
                   Element 
                   wt. % 
                   wt. % 
                 
                     
                     
                 
                     
                 
                 
                 
                 
                 
               
                     
                   Copper (Cu) 
                   0.00 
                   0.03 
                 
                     
                   Iron* (Fe) 
                   0.00 
                   0.20 
                 
                     
                   Magnesium (Mg) 
                   0.10 
                   0.60 
                 
                     
                   Manganese* (Mn) 
                   0.45 
                   0.80 
                 
                     
                   Phosphorus (P) 
                   0.00 
                   0.001 
                 
                     
                   Silicon (Si) 
                   7.00 
                   11.50 
                 
                     
                   Strontium (Sr) 
                   0.00 
                   0.03 
                 
                     
                   Titanium (Ti) 
                   0.00 
                   0.15 
                 
                     
                   Zinc (Zn) 
                   0.00 
                   0.07 
                 
                     
                   Individual Impurities 
                   0.00 
                   0.05 
                 
                     
                   Total Impurities 
                   0.00 
                   0.15 
                 
                 
                 
                 
               
                     
                   Aluminum (Al) 
                   Balance 
                 
                     
                     
                 
                     
                   wherein the wt. % Fe + the wt. % Mn < 0.95. 
                 
             
                
                
                
                
               
               
                
               
            
             
                
                
                
                
                
                
                
                
                
                
                
               
            
             
                
                
                
               
            
           
         
       
     
     
         2 . The method according to  claim 1  further comprising the step of exposing the HPDC material to a subsequent heat treatment step at about 180° C. for about 30 minutes. 
     
     
         3 . The method according to  claim 2 , wherein the subsequent heat treatment step results in a yield strength of at least about 80 MPa for an aluminum alloy. 
     
     
         4 . The method according to  claim 1 , wherein the eutectic silicon spheroidization comprises fewer than an average of about 3.50×10{circumflex over ( )}5 silicon particles per mm{circumflex over ( )}2 in any of the Al—Si eutectic microstructural constituents of the HPDC material. 
     
     
         5 . The method according to  claim 1 , wherein the temperature of the heat treatment step is 450° C. and the time period is between 10-30 minutes to result in full spheroidization of silicon eutectic,
 wherein there are fewer than about 1.50×10{circumflex over ( )}5 silicon particles per mm{circumflex over ( )}2 in any of the Al—Si eutectic microstructural constituents of an HPDC material. 
 
     
     
         6 . The method according to  claim 1 , wherein the temperature of the heat treatment step is between 300° C. to 450° C. and the time period is between 30 minutes to 2 hours to result in intermediate spheroidization of silicon eutectic,
 wherein there are between about 3.50×10{circumflex over ( )}5 and about 1.50×10{circumflex over ( )}5 silicon particles per mm{circumflex over ( )}2 in any of the Al—Si eutectic microstructural constituents of an HPDC material. 
 
     
     
         7 . The method according to  claim 1 , wherein the temperature of the heat treatment step is 300° C. and the time period is between 2 to 5 hours to result in partial spheroidization of silicon eutectic,
 wherein there are fewer than about 3.50×10{circumflex over ( )}5 silicon particles per mm{circumflex over ( )}2 in an HPDC material. 
 
     
     
         8 . The method according to  claim 1 , wherein the HPDC material is an aluminum alloy. 
     
     
         9 . The method according to  claim 1  further comprising a step of quenching the HPDC material after the heat treatment. 
     
     
         10 . The method according to  claim 1 , wherein the heat treatment are localized over predetermined portions of the HPDC material. 
     
     
         11 . The method according to  claim 1 , wherein the quenching is a forced air quench for a period of 6° C./s. 
     
     
         12 . A part formed according to the method of  claim 1 . 
     
     
         13 . A method of treating a high pressure die cast (HPDC) material to improve rivetability, the method comprising:
 exposing the HPDC material to a temperature between 300° C. and 450° C. for a time period between 10 minutes and 2 hours in an initial heat treatment step; and   exposing the HPDC material to a subsequent heat treatment step at about 180° C. for about 30 minutes after quenching,   wherein the heat treatment results in eutectic silicon spheroidization of the HPDC material such that the HPDC material does not crack after rivet installation and the subsequent heat treatment step increases yield strength of the HPDC material.   
     
     
         14 . The method according to  claim 13 , wherein the subsequent heat treatment step results in a yield strength of at least about 80 MPa for an aluminum alloy. 
     
     
         15 . The method according to  claim 13 , wherein the eutectic silicon spheroidization comprises fewer than an average of about 3.50×10{circumflex over ( )}5 silicon particles per mm{circumflex over ( )}2 in any of the Al—Si eutectic microstructural constituents of the HPDC material. 
     
     
         16 . The method according to  claim 13 , wherein the heat treatments are localized over predetermined portions of the HPDC material. 
     
     
         17 . A method of treating an aluminum high pressure die cast (HPDC) material to improve rivetability, the method comprising:
 exposing the aluminum HPDC material to a temperature between 300° C. and 450° C. for a time period between 10 minutes and 2 hours in an initial heat treatment step;   quenching the aluminum HPDC material; and   exposing the aluminum HPDC material to a subsequent heat treatment step at about 180° C. for about 30 minutes after quenching,   wherein the heat treatment results in eutectic silicon spheroidization of the aluminum HPDC material such that the aluminum HPDC material does not crack after rivet installation and the subsequent heat treatment step increases yield strength of the aluminum HPDC material to at least 80 MPa.   
     
     
         18 . The method according to  claim 17 , wherein the eutectic silicon spheroidization comprises fewer than an average of about 3.50×10{circumflex over ( )}5 silicon particles per mm{circumflex over ( )}2 in any of the Al—Si eutectic microstructural constituents of the HPDC material. 
     
     
         19 . The method according to  claim 17 , wherein the heat treatments and the quenching are localized over predetermined portions of the HPDC material. 
     
     
         20 . The method according to  claim 17 , wherein the quenching is a forced air quench for a period of 6° C./s.