Aluminum-silicon alloys having improved mechanical properties

Abstract

A thermal treatment process for an article of a cast or wrought aluminum-silicon alloy with an eutectic phase. The process comprises a rapid heating of the article to an annealing temperature of 400° C. to 555° C. and maintaining the article at this temperature for a not more than 14.8 minutes.

1 . A thermal treatment process for improving the material ductility of an article which comprises a cast or wrought aluminum-silicon alloy with an eutectic phase, which process comprises subjecting the article to an annealing treatment and a subsequent aging treatment, wherein the annealing treatment is carried out as a shock annealing treatment which comprises (a) a rapid heating of the material to an annealing temperature of 400° C. to 555° C., (b) maintaining the material at this temperature for a holding period of not more than 14.8 minutes, and (c) a subsequent forced cooling of the material to essentially room temperature. 
   
   
       2 . The process of  claim 1 , wherein the aluminum-silicon alloy further comprises one or more alloying elements. 
   
   
       3 . The process of  claim 1 , wherein the aluminum-silicon alloy further comprises one or more contaminating elements. 
   
   
       4 . The process of  claim 1 , wherein the aluminum-silicon alloy further comprises at least one of Mg, Mn and Fe. 
   
   
       5 . The process of  claim 1 , wherein the aluminum-silicon alloy is at least one of refined and purified. 
   
   
       6 . The process of  claim 1 , wherein the holding period is shorter than 6.8 minutes. 
   
   
       7 . The process of  claim 1 , wherein the holding period is not shorter than 1.7 minutes. 
   
   
       8 . The process of  claim 7 , wherein the holding period is not longer than 5 minutes. 
   
   
       9 . The process of  claim 1 , wherein the aging treatment comprises a treatment at a temperature of from 150° C. to 200° C. 
   
   
       10 . The process of  claim 9 , wherein the aging treatment is carried out for from 1 to 14 hours. 
   
   
       11 . The process of  claim 1 , wherein the aging treatment comprises a cold aging treatment at essentially room temperature. 
   
   
       12 . The process of  claim 1 , wherein the holding period is from 1.7 to less than 6.8 minutes and the aging treatment comprises a treatment at a temperature of from 150° C. to 200° for from 1 to 14 hours. 
   
   
       13 . The process of  claim 1 , wherein the holding period is from 1.7 to less than 6.8 minutes and the aging treatment comprises a cold aging treatment at essentially room temperature. 
   
   
       14 . The process if  claim 1 , wherein the article is made by a thixocasting method. 
   
   
       15 . The process if  claim 1 , wherein the entire article is subjected to the annealing treatment. 
   
   
       16 . The process if  claim 1 , wherein the eutectic phase consists essentially of an α Al -matrix and spheroidized silicon precipitates, which precipitates have an average cross-sectional area, A Si , of not more than 4 μm 2 , A Si  being represented by the following equation: 
     
       
         
           
             
               A 
               Si 
             
             = 
             
               
                 
                   1 
                   n 
                 
                  
                 
                   
                     ∑ 
                     
                       k 
                       = 
                       1 
                     
                     n 
                   
                    
                   A 
                 
               
               ≤ 
               
                 4 
                  
                 
                     
                 
                  
                 
                   µm 
                   2 
                 
               
             
           
         
       
     
     wherein
 A Si =average area of the silicon particles in μm 2    
 A=average area of the silicon particles per image, in μm 2    
 n=number of images sampled. 
 
   
   
       17 . The process of  claim 1 , wherein the eutectic phase consists essentially of an α Al -matrix and silicon precipitates, the silicon precipitates comprising silicon particles and an average free path length between the silicon particles, λ Si , in the eutectic phase being not higher than 4 μm, λ Si  being represented by the following equation: 
     
       
         
           
             
               λ 
               Si 
             
             = 
             
               
                 
                   1 
                   n 
                 
                  
                 
                   
                     ∑ 
                     
                       k 
                       = 
                       1 
                     
                     n 
                   
                    
                   
                     
                       
                         A 
                         square 
                       
                       
                         N 
                         Silicon 
                       
                     
                   
                 
               
               ≤ 
               
                 4 
                  
                 
                     
                 
                  
                 µm 
               
             
           
         
       
     
     wherein
 λ Si =average spacing between the silicon particles 
 A square =square reference area in μm 2    
 N Silicon =number of silicon particles 
 n=number of images sampled. 
 
   
   
       18 . The process of  claim 1 , wherein the the eutectic phase consists essentially of an α Al -matrix and silicon precipitates, which silicon precipitates comprise silicon particles and an average spheroidization density, ζ Si , thereof, defined as a number of silicon particles per 100 μm 2 , is at least 10: 
     
       
         
           
             
               ξ 
               Si 
             
             = 
             
               
                 
                   1 
                   n 
                 
                  
                 
                   
                     ∑ 
                     
                       k 
                       = 
                       1 
                     
                     n 
                   
                    
                   
                     
                       
                         N 
                         Si 
                       
                       A 
                     
                     × 
                     100 
                   
                 
               
               ≥ 
               10 
             
           
         
       
     
     wherein
 ζ Si =average spheroidization density of the eutectic Si particles 
 N Si =number of silicon particles 
 A=reference area in μm 2    
 n=number of images sampled. 
 
   
   
       19 . A thermal treatment process for improving the material ductility of an article which comprises a cast or wrought aluminum-silicon alloy with an eutectic phase, which process comprises subjecting the entire article to an annealing treatment and a subsequent aging treatment, wherein the annealing treatment is carried out as a shock annealing treatment which comprises (a) a rapid heating of the material to an annealing temperature of 400° C. to 555° C., (b) maintaining the material at this temperature for a holding period of not more than 5.8 minutes, and (c) a subsequent forced cooling of the material to essentially room temperature. 
   
   
       20 . The process of  claim 19 , wherein the holding period is not longer than 5 minutes.