Thixomolding material, method for manufacturing thixomolding material, and thixomolded article

Abstract

A thixomolding material includes: a metal body that contains Mg as a main component; and a coating portion that is adhered to a surface of the metal body via a binder and contains SiO2 particles containing SiO2 as a main component. An average particle diameter of the SiO2 particles is less than 20.0 μm, and a mass fraction of the SiO2 particles in a total mass of the metal body and the SiO2 particles is 1.0 mass % or more and 40.0 mass % or less. The binder may contain waxes. A content of the binder may be 0.001 mass % or more and 0.200 mass % or less.

What is claimed is: 
     
         1 . A thixomolding material comprising:
 a metal body that contains Mg as a main component; and   a coating portion that is adhered to a surface of the metal body via a binder and contains SiO 2  particles containing SiO 2  as a main component, wherein   an average particle diameter of the SiO 2  particles is less than 20.0 μm, and   a mass fraction of the SiO 2  particles in a total mass of the metal body and the SiO 2  particles is 1.0 mass % or more and 40.0 mass % or less.   
     
     
         2 . The thixomolding material according to  claim 1 , wherein the binder contains waxes. 
     
     
         3 . The thixomolding material according to  claim 1 , wherein a content of the binder is 0.001 mass % or more and 0.200 mass % or less. 
     
     
         4 . A method for manufacturing a thixomolding material, comprising:
 a preparation step of preparing a mixture containing a metal body containing Mg as a main component, SiO 2  particles containing SiO 2  as a main component, a binder, and a solvent;   a stirring step of stirring the mixture; and   a debindering step of removing, by heating the stirred mixture, at least a part of the binder contained in the mixture to obtain a thixomolding material, wherein   a mass fraction of the SiO 2  particles in a total mass of the metal body and the SiO 2  particles is 1.0 mass % or more and 40.0 mass % or less, and   a content of the binder in the thixomolding material is 0.001 mass % or more and 0.200 mass % or less.   
     
     
         5 . A thixomolded article comprising:
 a matrix portion that contains Mg as a main component,   a first particle portion that is dispersed in the matrix portion and contains Mg 2 Si as a main component; and   a second particle portion that is dispersed in the matrix portion, present independently of the first particle portion, and contains MgO as a main component, wherein   when observing a cross section, a total area fraction of the first particle portion and the second particle portion, in a range of 500 μm square centered on a point at a depth of 1 mm from a surface, is 1.0% or more and 55.0% or less.   
     
     
         6 . The thixomolded article according to  claim 5 , wherein when observing the cross section, |As−Ac|/Ac is 50.0% or less where As [%] is a total area fraction of the first particle portion and the second particle portion in a range of 500 μm square starting from the surface, and Ac [%] is a total area fraction of the first particle portion and the second particle portion in a range of 500 μm square centered on the point at a depth of 1 mm from the surface. 
     
     
         7 . The thixomolded article according to  claim 5 , wherein an average particle diameter ratio D(Mg 2 Si)/D(MgO) is 0.4 or more and 2.0 or less where D(Mg 2 Si) is an average particle diameter of the first particle portion and D(MgO) is an average particle diameter of the second particle portion. 
     
     
         8 . The thixomolded article according to  claim 5 , wherein
 a tensile strength is 180 MPa or more and 300 MPa or less, and   a Young's modulus is 43 GPa or more and 80 GPa or less.