Aluminum alloy substrate for magnetic recording medium and method for manufacturing the same, substrate for magnetic recording medium, magnetic recording medium, and hard disc drive
This aluminum alloy substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 18.0% by mass to 22.0% by mass, Ni in a range of 5.0% by mass to 8.5% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al, a primary-crystal Si precipitate having a maximum diameter of 0.5 μm or more and an average particle diameter of 2 μm or less is dispersed in the metal structure, a diameter is in a range of 53 mm to 97 mm, and a thickness is in a range of 0.2 mm to 0.9 mm.
1. An aluminum alloy substrate for a magnetic recording medium, having
a metallic structure made of an Al alloy which has a composition including Si in a range of 18.0% by mass to 22.0% by mass, Ni in a range of 5.0% by mass to 8.5% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al,
wherein primary-crystal Si particles which have a maximum diameter of 0.5 μm or more and an average particle diameter of 2 μm or less are dispersed in the metallic structure,
a diameter of the substrate is in a range of 53 mm to 97 mm, and a thickness of the substrate is in a range of 0.2 mm to 0.9 mm, and
a value of E/ρ (E: Young's modulus, ρ: density) is 36.0 (GPa)/(gcm −3 ) or more.
2. The aluminum alloy substrate for a magnetic recording medium according to claim 1 ,
wherein the Al alloy further includes Zn in a range of 0.01% by mass to 0.5% by mass.
3. The aluminum alloy substrate for a magnetic recording medium according to claim 1 ,
wherein the Al alloy further includes one or more of Mn, Ti, Cr, V, Zr, Mo, and Co in a range of 0.01% by mass to 0.5% by mass.
4. The aluminum alloy substrate for a magnetic recording medium according to claim 1 ,
wherein an Al—Ni-based intermetallic compound is dispersed in the metal structure.
5. The aluminum alloy substrate for a magnetic recording medium according to claim 1 ,
wherein the metal structure is an extruded structure of a powder particle compact of the Al alloy.
6. A substrate for a magnetic recording medium, comprising:
an aluminum alloy substrate; and
a NiP-based plating coat formed on at least one surface of the aluminum alloy substrate,
wherein the aluminum alloy substrate is the aluminum alloy substrate for a magnetic recording medium according to claim 1 .
7. A magnetic recording medium comprising:
a substrate for a magnetic recording medium; and
a magnetic layer provided on a surface of the substrate for a magnetic recording medium,
wherein the substrate for a magnetic recording medium is the substrate for a magnetic recording medium according to claim 6 , and
the magnetic layer is provided on the surface of the substrate for a magnetic recording medium on which the NiP-based plating coat is formed.
8. A hard disc drive equipped with a magnetic recording medium,
wherein the magnetic recording medium is the magnetic recording medium according to claim 7 .
9. A method for manufacturing the aluminum alloy substrate for a magnetic recording medium according to claim 1 , the method comprising:
forming a compact of powder particles made of an Al alloy having a composition including Si in a range of 18.0% by mass to 22.0% by mass, Ni in a range of 5.0% by mass to 8.5% by mass, Cu in a range of 2.5% by mass to 4.0% by mass, and Mg in a range of 0.8% by mass to 1.5% by mass with a remainder being Al;
extruding this compact to form a cylindrical body; and
cutting this cylindrical body to obtain a disc-shaped aluminum alloy substrate for a magnetic recording medium from the cylindrical.
10. The method for manufacturing an aluminum alloy substrate for a magnetic recording medium according to claim 9 ,
wherein the Al alloy further includes Zn in a range of 0.01% by mass to 0.5% by mass.
11. The method for manufacturing an aluminum alloy substrate for a magnetic recording medium according to claim 9 ,
wherein the Al alloy further includes one or more of Mn, Ti, Cr, V, Zr, Mo, and Co in a range of 0.01% by mass to 0.5% by mass.
12. The method for manufacturing an aluminum alloy substrate for a magnetic recording medium according to claim 9 ,
wherein a primary-crystal Si precipitate having a maximum diameter of 0.5 μm or more and an average particle diameter of 2 μm or less is dispersed in the powder particle.
13. The aluminum alloy substrate for a magnetic recording medium according to claim 1 , wherein the Al alloy including Si in a range of 19.0% by mass to 21.5% by mass, Ni in a range of 6.5% by mass to 8.0% by mass, Cu in a range of 3.0% by mass to 3.8% by mass, and Mg in a range of 1.0% by mass to 1.4% by mass with a remainder being Al.