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 . An article which is obtainable by the process of  claim 1 .  
     
     
         16 . An article comprising an aluminum-silicon alloy with an eutectic phase, 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 
                   ⁢ 
                   μ 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     m 
                     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 article of  claim 16 , wherein A Si  is less than 2 μm 2 .  
     
     
         18 . The article of  claim 16 , wherein the aluminum-silicon alloy further comprises at least one of one or more alloying elements and one or more contaminating elements.  
     
     
         19 . The article of  claim 18 , wherein the aluminum-silicon alloy further comprises at least one of Mg, Mn and Fe.  
     
     
         20 . The article of  claim 16 , wherein the aluminum-silicon alloy further comprises at least one processing element.  
     
     
         21 . An article comprising an aluminum-silicon alloy with an eutectic phase, wherein the eutectic phase consists essentially of an α Al -matrix and silicon precipitates, wherein the silicon precipitates comprise silicon particles and an average free path length between the silicon particles, λ Si , in the eutectic phase is 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 
                   ⁢ 
                   μ 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   m 
                 
               
             
           
         
         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.  
       
     
     
         22 . The article of  claim 21 , wherein the average free path length is less than 3 μm.  
     
     
         23 . The article of  claim 22 , wherein the average free path length is less than 2 μm.  
     
     
         24 . The article of  claim 21 , wherein the aluminum-silicon alloy further comprises at least one of one or more alloying elements and one or more contaminating elements.  
     
     
         25 . The article of  claim 24 , wherein the aluminum-silicon alloy further comprises at least one of Mg, Mn and Fe.  
     
     
         26 . The article of  claim 21 , wherein the aluminum-silicon alloy further comprises at least one processing element.  
     
     
         27 . An article comprising an aluminum-silicon alloy with an eutectic phase, wherein the eutectic phase consists essentially of an α Al -matrix and silicon precipitates, wherein the 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.  
 
     
     
         28 . The article of  claim 27 , wherein the average spheroidization density is greater than 20.  
     
     
         29 . The article of  claim 27 , wherein the aluminum-silicon alloy farther comprises at least one of one or more alloying elements and one or more contaminating elements.  
     
     
         30 . The article of  claim 29 , wherein the aluminum-silicon alloy further comprises at least one of Mg, Mn and Fe.  
     
     
         31 . The article of  claim 27 , wherein the aluminum-silicon alloy further comprises at least one processing element.  
     
     
         32 . The article of  claim 16 , wherein the article is made by a thixocasting method and is heat treated by a process which comprises subjecting the article to an annealing treatment and a subsequent aging treatment, the annealing treatment being carried out as a shock annealing treatment which comprises (a) a rapid heating of the article to an annealing temperature of 400° C. to 555° C., (b) maintaining the article at this temperature for a holding period of not more than 14.8 minutes, and (c) a subsequent forced cooling of the article to essentially room temperature.  
     
     
         33 . The article of  claim 21 , wherein the article is made by a thixocasting method and is heat treated by a process which comprises subjecting the article to an annealing treatment and a subsequent aging treatment, the annealing treatment being carried out as a shock annealing treatment which comprises (a) a rapid heating of the article to an annealing temperature of 400° C. to 555° C., (b) maintaining the article at this temperature for a holding period of not more than 14.8 minutes, and (c) a subsequent forced cooling of the article to essentially room temperature.  
     
     
         34 . The article of  claim 27 , wherein the article is made by a thixocasting method and is heat treated by a process which comprises subjecting the article to an annealing treatment and a subsequent aging treatment, the annealing treatment being carried out as a shock annealing treatment which comprises (a) a rapid heating of the article to an annealing temperature of 400° C. to 555° C., (b) maintaining the article at this temperature for a holding period of not more than 14.8 minutes, and (c) a subsequent forced cooling of the article to essentially room temperature.