Magnesium alloy sheet and manufacturing method therefor

Abstract

A magnesium alloy sheet containing, relative to 100 wt % of the entire magnesium alloy sheet, 2.7 to 5.0 wt % of Al, 0.75 to 1.0 wt % of Zn, 0.1 to 1.0 wt % of Ca, 1.0 wt % or less of Mn (excluding 0 wt %), and the balance of Mg and other inevitable impurities, wherein a volume fraction of bottom crystal grains, relative to 100 vol % of overall crystal grains of the magnesium alloy sheet, is 30% or less, and the bottom crystal grains are crystal grains in a <0001>//C-axis direction.

1 . A magnesium alloy sheet comprising: relative to 100 wt % of the entire magnesium alloy sheet, 2.7 to 5.0 wt % of Al, 0.75 to 1.0 wt % of Zn, 0.1 to 1.0 wt % of Ca, 1.0 wt % or less of Mn (excluding 0 wt %), and the balance of Mg and other inevitable impurities,
 wherein a volume fraction of bottom crystal grains is 30% or less relative to 100 vol % of overall crystal grains of the magnesium alloy sheet, and   wherein the bottom crystal grains are crystal grains in a <0001>//C-axis direction.   
     
     
         2 . The magnesium alloy sheet of  claim 1 , wherein:
 the magnesium alloy sheet comprises Al—Ca secondary phase particles, and   a difference in area fraction of the Al—Ca secondary phase particles is 10% or less between a quarter portion (¼) of a surface of the magnesium alloy sheet and a center portion (½) of the surface of the magnesium alloy sheet.   
     
     
         3 . The magnesium alloy sheet of  claim 2 , wherein:
 a ratio of a length of center segregation to a total length of the magnesium alloy sheet in a rolling direction is less than 5%.   
     
     
         4 . The magnesium alloy sheet of  claim 3 , wherein:
 a ratio of a thickness of the center segregation to a total thickness of the magnesium alloy sheet in a thickness direction is less than 2.5%.   
     
     
         5 . The magnesium alloy sheet of  claim 4 , wherein:
 a limiting dome height (LDH) of the magnesium alloy sheet is 7 mm or more, and   a maximum texture intensity of a (0001) surface of the magnesium alloy sheet is 1 to 4.   
     
     
         6 . A magnesium alloy sheet comprising: relative to 100 wt % of the entire magnesium alloy sheet, 2.7 to 5.0 wt % of Al, 0.75 to 1.0 wt % of Zn, 0.1 to 1.0 wt % of Ca, 1.0 wt % or less of Mn (excluding 0 wt %), and the balance of Mg and other inevitable impurities,
 wherein a volume fraction of a twinned crystal structure is 35% or less relative to 100 vol % of the entire area of the magnesium alloy sheet.   
     
     
         7 . The magnesium alloy sheet of  claim 6 , wherein:
 the volume fraction of the twinned crystal structure, relative to 100 vol % of the entire area of the magnesium alloy sheet, is 5 to 35%.   
     
     
         8 . The magnesium alloy sheet of  claim 7 , wherein:
 a volume fraction of bottom crystal grains is 30% or less relative to 100 vol % of overall crystal grains of the magnesium alloy sheet, and   the bottom crystal grains are crystal grains in a <0001>//C-axis direction.   
     
     
         9 . The magnesium alloy sheet of  claim 8 , wherein:
 a limiting dome height of the magnesium alloy sheet is 7 mm or more, and   a maximum texture intensity of a (0001) surface of the magnesium alloy sheet is 1 to 4.   
     
     
         10 . The magnesium alloy sheet of  claim 9 , wherein:
 a yield strength of the magnesium alloy sheet is 200 to 300 MPa.