Magnesium alloy sheet and magnesium alloy structural member

Abstract

Provided are a magnesium alloy sheet having excellent formability in plastic forming, such as press forming, and a magnesium alloy structural member. The magnesium alloy sheet is obtained by subjecting a magnesium alloy to rolling and has a cross section parallel to the thickness direction of the magnesium alloy sheet, in which, when the length of the major axis and the length of the minor axis of each of crystal grains in the cross section are determined, an aspect ratio is defined as the ratio of the length of the major axis to the length of the minor axis (length of major axis/length of minor axis), and crystal grains having an aspect ratio of 3.85 or more are defined as elongated grains, the area fraction of the elongated grains in the cross section is 3% to 20%.

1 . A magnesium alloy sheet obtained by subjecting a magnesium alloy to rolling, and having a cross section parallel to the thickness direction of the magnesium alloy sheet in which the area fraction of elongated grains in the cross section is 3% to 20%, where the elongated grains are defined as crystal grains having an aspect ratio of 3.85 or more in the cross section when the length of the major axis and the length of the minor axis of each of crystal grains in the cross section are determined, and the aspect ratio is defined as the ratio of the length of the major axis to the length of the minor axis. 
     
     
         2 . The magnesium alloy sheet according to  claim 1 , wherein, when a pole figure of (0001) planes of the elongated grains is taken, crystal grains with the angle θ TD  in the sheet width direction in the (0001) planes of the elongated grains within 5° are selected, and the angle θ RD  in the rolling direction in the (0001) planes of the selected crystal grains is checked, the peak of the angle θ RD  in the rolling direction is present at 9° or more from the normal direction. 
     
     
         3 . The magnesium alloy sheet according to  claim 1 , wherein, when a pole figure of (0001) planes of the elongated grains is taken, crystal grains with the angle θ RD  in the rolling direction in the (0001) planes of the elongated grains within 20° are selected, and the angle θ TO  in the sheet width direction in the (0001) planes of the selected crystal grains is checked, the total area fraction of crystal grains with the angle θ TD  in the sheet width direction from the normal direction being −20° or less and crystal grains with the angle θ TD  in the sheet width direction from the normal direction being +20° or more is 20% to 70% relative to all the elongated grains. 
     
     
         4 . The magnesium alloy sheet according to  claim 1 , wherein the average cross-sectional area of the elongated grains is 600 μm 2  or less. 
     
     
         5 . The magnesium alloy sheet according to  claim 1 , wherein the magnesium alloy contains 8.3% to 9.5% by mass of Al. 
     
     
         6 . The magnesium alloy sheet according to  claim 1 , wherein the cross-sectional area of each of the elongated grains is more than 25 μm 2  and 5,000 μm 2  or less. 
     
     
         7 . A magnesium alloy structural member obtained by subjecting at least part of the magnesium alloy sheet according to  claim 1  to press forming.