Magnesium alloy material and method for producing the same

Abstract

There are provided a magnesium alloy material and a method for producing the magnesium alloy material. In a magnesium (Mg) alloy material (e.g., Mg alloy sheet) having a sheet-shaped portion with a thickness of 1.5 mm or more, when a region having ¼ the thickness of the sheet-shaped portion in a thickness direction from a surface of the sheet-shaped portion is defined as a surface region and a remaining region is defined as an internal region, the ratio O F /O C of the basal plane peak ratio O F in the surface region to the basal plane peak ratio O C (degree of orientation of (002) planes) in the internal region satisfies 1.05<O F /O C . A sheet-shaped Mg alloy material is obtained by performing rolling on a twin-roll continuous cast material with multiple passes at a reduction ratio of each pass of 25% or less.

1 . A magnesium alloy material composed of a magnesium alloy, comprising a sheet-shaped portion,
 wherein the sheet-shaped portion has a thickness of 1.5 mm or more, and   the sheet-shaped portion satisfies the following orientation,   
       [Orientation]
 when a region having ¼ the thickness of the sheet-shaped portion in a thickness direction from a surface of the sheet-shaped portion is defined as a surface region and a remaining region is defined as an internal region, 
 X-ray diffraction peak intensities of a (002) plane, a (100) plane, a (101) plane, a (102) plane, a (110) plane, and a (103) plane in the surface region are respectively defined as I F (002), I F (100), I F (101), I F (102), I F (110), and I F (103), 
 X-ray diffraction peak intensities of a (002) plane, a (100) plane, a (101) plane, a (102) plane, a (110) plane, and a (103) plane in the internal region are respectively defined as I C (002), I C (100), I C (101), I C (102), I C (110), and I C (103), 
 a degree of orientation of the (002) plane in the surface region, which is expressed as I F (002)/{I F (100)+I F (002)+I F (101)+I F (102)+I F (110)+I F (103)}, is defined as a basal plane peak ratio O F , and 
 a degree of orientation of the (002) plane in the internal region, which is expressed as I C (002)/{I C (100)+I C (002)+I C (101)+I C (102)+I C (110)+I C (103)}, is defined as a basal plane peak ratio O C , 
 a ratio O F /O C  of the basal plane peak ratio O F  in the surface region to the basal plane peak ratio O C  in the internal region satisfies 1.05<O F /O C . 
 
     
     
         2 . The magnesium alloy material according to  claim 1 , wherein, when an average crystal grain size in the surface region is defined as D F  and an average crystal grain size in the internal region is defined as D C , a ratio D C /D F  of the average crystal grain size D C  in the internal region to the average crystal grain size D F  in the surface region satisfies 1.5<D C /D F . 
     
     
         3 . The magnesium alloy material according to  claim 1 , wherein, when a Vickers hardness (Hv) in the surface region is defined as H F  and a Vickers hardness (Hv) in the internal region is defined as H C , a ratio H C /H F  of the Vickers hardness H C  in the internal region to the Vickers hardness H F  in the surface region satisfies H C /H F <0.85. 
     
     
         4 . The magnesium alloy material according to  claim 1 , wherein the magnesium alloy contains Al as an additive element in a content of 5.0 mass % or more and 12 mass % or less. 
     
     
         5 . A method for producing a magnesium alloy material by rolling a raw material composed of a magnesium alloy, the method comprising:
 a preparation step of preparing a sheet-shaped raw material obtained by subjecting a molten magnesium alloy to continuous casting by a twin-roll casting process; and   a rolling step of rolling the raw material with multiple passes to produce a sheet-shaped magnesium alloy material having a thickness of 1.5 mm or more,   wherein a reduction ratio of each of the passes is 25% or less.   
     
     
         6 . The magnesium alloy material according to  claim 2 , wherein, when a Vickers hardness (Hv) in the surface region is defined as H F  and a Vickers hardness (Hv) in the internal region is defined as H C , a ratio H C /H F  of the Vickers hardness H C  in the internal region to the Vickers hardness H F  in the surface region satisfies H C /H F <0.85. 
     
     
         7 . The magnesium alloy material according to  claim 2 , wherein the magnesium alloy contains Al as an additive element in a content of 5.0 mass % or more and 12 mass % or less. 
     
     
         8 . The magnesium alloy material according to  claim 3 , wherein the magnesium alloy contains Al as an additive element in a content of 5.0 mass % or more and 12 mass % or less. 
     
     
         9 . The magnesium alloy material according to  claim 4 , wherein the magnesium alloy contains Al as an additive element in a content of 5.0 mass % or more and 12 mass % or less. 
     
     
         10 . The magnesium alloy material according to  claim 6 , wherein the magnesium alloy contains Al as an additive element in a content of 5.0 mass % or more and 12 mass % or less.