Aluminum Alloy Substrates for Magnetic Disks

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For HDD Magnetic Disks

Picture of Aluminum Alloy Substrates for Magnetic Disks

Magnetic disks made of aluminum alloys are used in hard disk drives (HDDs) because aluminum is non-magnetic, lightweight and grindable precisely. Aluminum substrates are less expensive than glass substrates, so they are used not only in personal computers but also in home electronics such as HDD recorders.


  • Our optimum casting and heat treatment conditions limit intermetallic compounds and non-metallic inclusions which cause surface defects on magnetic disks.
  • Excellent flatness necessary for magnetic disks is attained by our sophisticated manufacturing technology and quality control.

Product Characteristics

Chemical composition and characteristics of FP-3 alloy

Chemical composition (mass%)

Si Fe Cu Mn Mg Cr Zn Ti Al
≦0.05 ≦0.1 ≦0.05 ≦0.1 3.5–5.0 ≦0.1 ≦0.5 ≦0.1 bal.


Tensile strength
Yield strength
Specific gravity Young's modulus
Thermal expansion coefficient
250 120 23 60 2.65 72 24.2

Production Process

Magnetic disk production process (abbreviated)

Fig. Magnetic disk production process (abbreviated)