Aluminum alloy forging material and method for manufacturing same

Abstract

Provided are a 6000-series aluminum alloy forging material having high strength and exceptional toughness (excellent ductility), and an efficient method for manufacturing the same. This aluminum alloy forging material is characterized by being formed from a 6000-series aluminum alloy, having a Cu content of 0.2-1.0 wt. %, the composition of the 6000-series aluminum alloy satisfying relational expressions (1) and (2), and having deposits at the base metal crystal grain boundary, specifically Al—(Fe,Mn,Cr)—Si-type crystalline deposits at the base metal crystal grain boundary. (1) Si (at %)≥2Mg (at %) and (2) 0.2≤surplus Si (wt %)+Mn (wt %)+Cr (wt %)≤1.7.

1 . An aluminum alloy forging material characterized by being formed from a 6000 series aluminum alloy, having a Cu content of 0.2 to 1.0 wt %, the composition of the 6000 series aluminum alloy satisfying the following relational equations (1) and (2), and having precipitates in the base metal crystal grain boundary, and an Al—(Fe, Mn, Cr)—Si-based crystal precipitates in the base metal crystal grain.
   Si(at %)≥2Mg(at %)  (1)
 
   0.2≤excess Si(wt %)+Mn(wt %)+Cr(wt %)≤1.7  (2)
 
 
     
     
         2 . The aluminum alloy forging material according to  claim 1 , wherein the content of Si is 0.5 to 1.4 wt %, and the content of Mg is 0.6 to 1.7 wt %. 
     
     
         3 . The aluminum alloy forging material according to  claim 1 , wherein the content of Si is 0.9 to 1.2 wt %, and the content of Mg is 0.8 to 1.2 wt %. 
     
     
         4 . The aluminum alloy forging material according to  claim 1 , wherein the average grain size of the precipitate in the crystal grain boundary of the base material is 50 nm or less. 
     
     
         5 . The aluminum alloy forging material according to  claim 1 , wherein the aspect ratio of the precipitate in the crystal grain boundary of the base material is 5 or less. 
     
     
         6 . The aluminum alloy forging material according to  claim 1 , wherein the width of the precipitation-free zone centering on the crystal grain boundary of the base material is 100 nm or less. 
     
     
         7 . The aluminum alloy forging material according to  claim 1 , wherein the 0.2% proof stress is 350 MPa or more and the elongation is 10% or more. 
     
     
         8 . An automotive underbody part characterized by comprising the aluminum alloy forging material according to  claim 1 . 
     
     
         9 . A method for manufacturing the aluminum alloy forging material according to  claim 1 , characterized by
 setting the content of Cu in the aluminum alloy forging material to 0.2 to 1.0 wt %, and   including a hot forging preheating step of preheating the aluminum alloy material, and   a hot forging step of subjecting the preheated aluminum alloy material obtained in the hot forging preheating step to hot forging,   wherein the preheating temperature in the hot forging preheating step is 300 to 550° C. and the preheating time is 1 to 3 hours, and   the composition of the aluminum alloy satisfies the following relational equations (1) and (2).
   Si(at %)≥2Mg(at %)  (1)
 
   0.2≤excess Si(wt %)+Mn(wt %)+Cr(wt %)≤1.7  (2)
 
   
     
     
         10 . The method for manufacturing the aluminum alloy according to  claim 9 , wherein, a homogenization heat treatment step for the aluminum alloy material before the hot forging preheating step, and
 the temperature in the homogenization heat treatment step is 500 to 550° C. and the holding time is 5 to 10 hours.