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 m or more and an average particle diameter of 2 m 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.

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 m or more and an average particle diameter of 2 m 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.

This substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 28.0% by mass to 32.0% 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, primary-crystal Si particles having a maximum diameter of 0.5 m or more and an average particle diameter of 2 m 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.

This substrate for a magnetic recording medium has a metal structure made of an Al alloy having a composition including Si in a range of 28.0% by mass to 32.0% 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, primary-crystal Si particles having a maximum diameter of 0.5 m or more and an average particle diameter of 2 m 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.