Reduced final grain size of unrecrystallized wrought material produced via the direct chill (dc) route

Abstract

Grain size of a deliverable metal product can be improved by pre-setting recrystallization-suppressing dispersoids during casting. The outer regions of a direct chill cast embryonic ingot can undergo reheating before casting is complete. Through unique wiper placement and/or other reheating techniques, the temperature of the ingot can be permitted to reheat (e.g., up to approximately 410° C. to approximately 420° C.), allowing dispersoids to form. Stirring and/or agitation of the molten sump can facilitate formation of a deeper sump and desirably fine grain size as-cast. The formation of dispersoids during and/or immediately after casting can pin the grain boundaries at the desirably fine grain size, encouraging the same grain sizes even after a later recrystallization and/or solutionizing step.

What is claimed is: 
     
         1 . An aluminum metal product, comprising:
 a mass of solidified aluminum alloy having two ends and an outer surface, wherein the mass of solidified aluminum alloy comprises:
 a core region containing a center of the mass of solidified aluminum alloy; 
 an outer region incorporating the outer surface; and 
 a high-strength zone disposed between the core region and the outer region, wherein the high-strength zone has a higher concentration of dispersoids than each of the core region and the outer region. 
   
     
     
         2 . The aluminum metal product of  claim 1 , wherein the mass of solidified aluminum alloy comprises retained heat from a direct chill casting process. 
     
     
         3 . The aluminum metal product of  claim 1 , wherein the high-strength zone is located at a depth of approximately one third of a line extending from the outer surface to the center of the mass of solidified aluminum alloy along a cross section of the mass of solidified aluminum alloy. 
     
     
         4 . The aluminum metal product of  claim 1 , wherein the high-strength zone is located at a depth of no more than one half of a line extending from the outer surface to the center of the mass of solidified aluminum alloy along a cross section of the mass of solidified aluminum alloy. 
     
     
         5 . The aluminum metal product of  claim 1 , wherein the mass of solidified aluminum alloy is cylindrical in shape. 
     
     
         6 . The aluminum metal product of  claim 1 , wherein a cross section of the mass of solidified aluminum alloy that is perpendicular to a direction of casting of the mass of solidified aluminum alloy is rectangular in shape. 
     
     
         7 . The aluminum metal product of  claim 1 , wherein the mass of solidified aluminum alloy is a mass of solidified series 7xxx aluminum alloy.