Method for Preparing Nano-SiO2 Reinforced Aluminum Matrix Composites

Abstract

A method for preparing nano-SiO 2 reinforced aluminum matrix composites, includes the following: Step-1, powder mixing: mixing aluminum matrix powder with nano-SiO 2 powder to obtain raw material powder, wherein the aluminum matrix powder has an average particle size between 30 μm to 100 μm, the nano-SiO 2 powder has an average particle size between 5 nm to 145 nm, mass percentage of nano-SiO 2 in the raw material powder is 0.01% to 5% and the remaining raw material powder is the aluminum matrix powder; Step-2, shaping: press shaping the powder obtained in the Step-1 to obtain base bodies; Step-3, sintering: sintering the base bodies obtained in the Step-2 in an atmosphere of N 2 at 550° C. to 660° C., preserving the temperature for a period of 5 min to 60 min, and cooling in a furnace at end of the period under protection of N 2 for 0.5 h to 3 h; and Step-4, heat treatment.

1 . A method for preparing nano-SiO 2  reinforced aluminum matrix composites, comprising the following steps of:
 Step-1, powder mixing: mixing aluminum matrix powder with nano-SiO 2  powder to obtain raw material powder, the raw material powder being uniformly mixed, wherein the aluminum matrix powder has an average particle size between 30 μm to 100 μm, the nano-SiO 2  powder has an average particle size between 5 nm to 145 nm, mass percentage of nano-SiO 2  in the raw material powder is 0.01% to 5% and remaining of the raw material powder is the aluminum matrix powder, and the aluminum matrix powder is elemental aluminum powder, aluminum alloy powder, or aluminum matrix composite powder;   Step-2, shaping: press shaping the powder obtained in the Step-1 to obtain base bodies;   Step-3, sintering: sintering the base bodies obtained in the Step-2 in an atmosphere of N2 at 550° C. to 660° C., preserving the temperature for a period of 5 min to 60 min, and cooling in a furnace at end of the period under protection of N2 for 0.5 h to 3 h; and   Step-4: successively performing solid solution and artificial aging heat treatment on the sintered blanks of the Step-3, where the temperature for the solid solution is 450° C. to 580° C., the time for the solid solution is 0.5 h to 6 h, the temperature for the artificial aging is 100° C. to 200° C. and the time for the artificial aging is 3 h to 24 h.   
     
     
         2 . The method of  claim 1 , wherein in the Step-1, the average particle size of the aluminum matrix powder is 60 μm to 80 μm, the average particle size of the nano-SiO 2  powder is 10 nm to 50 nm, the mass percentage of the nano-SiO 2  powder in the raw material powder is 0.1% to 1.5%. 
     
     
         3 . The method of  claim 1 , wherein the powder mixing in the Step-1 is done by a ball mill, a rotation speed of the ball mill is 180 r/min to 230 r/min, and the time for ball milling is 4 h to 8 h. 
     
     
         4 . The method of  claim 3 , wherein the rotation speed of the ball mill is 180 r/min to 210 r/min, and the time for ball milling is 5 h to 6 h. 
     
     
         5 . The method of  claim 1 , wherein the nano-SiO 2  powder in the Step-1 is hydrophobic gas-phase silicon dioxide having main parameters shown in the following table: 
       
         
           
                 
                 
                 
               
                     
                 
                   Property 
                   Unit 
                   Typical value 
                 
                     
                 
                   Specific surface area (BET) 
                   m 2 /g 
                   110 ± 20 
                 
                   Bulk density* 
                   g/l 
                   50 
                 
                   in accordance with DIN EN ISO 787/11, 
                 
                   August 1983 
                 
                   Carbon 
                   Wt. % 
                   0.6~1.2 
                 
                   Average particle size of primary 
                   nm 
                   16 
                 
                   particles 
                 
                   Moisture content: dried for 2 h at 105° C. 
                   Wt. % 
                   ≤0.5 
                 
                   Loss on ignition: the material dried for 
                   Wt. % 
                   ≤2.0 
                 
                   2 h at 105° C. is burnt for 2 h at 1000° C. 
                 
                   pH value: in a 4% dispersoid 
                   Wt. % 
                   3.6-4.4 
                 
                   SiO 2  content: for the burnt material 
                   Wt. % 
                   ≥99.8 
                 
                     
                 
             
                
                
                
               
               
                
                
                
                
                
                
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         6 . The method of  claim 1 , wherein in the powder mixing of the Step-1, a lubricant is added in the raw material powder, wherein the mass of the lubricant is 0.5% to 2% of the mass of the raw material powder. 
     
     
         7 . The method of  claim 6 , wherein the lubricant is added manually or by a mixer, wherein the mixer is any one of a ball mill, a V-type mixer, a conical mixer, a barrel mixer and a helical mixer. 
     
     
         8 . The method of  claim 6  or  claim 7 , wherein the base bodies are dewaxed for 20 min to 50 min at 350° C. to 450° C. before the sintering in the Step-3. 
     
     
         9 . The method of  claim 1 , wherein in the Step-2, the press shaping method of the raw material powder is die shaping, and the pressure for shaping is 150 MPa to 500 MPa. 
     
     
         10 . The method of  claim 1 , wherein the Step-4 will not be performed when the sinter is an elemental aluminum matrix or a non-heat-treatable aluminum alloy matrix.