Al Alloy Substrate for HDD Base Reducing Fluttering
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Solution Overview
Problem
Magnetic recording media in HDDs face challenges with fluttering when the thickness of the base is reduced, leading to instability in reading information, especially with Al alloy substrates, which have higher toughness but are more prone to fluttering compared to glass substrates.
Innovation Solution
A base for magnetic recording media is developed using an Al alloy substrate with specific compositions of Si, Mn, Zn, Sr, Cu, and Zr, resulting in a Young's modulus of 79 GPa or higher, and a NiP-based alloy film with a thickness of 7 μm or greater, to reduce fluttering and improve machinability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the Al alloy substrate is reduced to increase the number of magnetic recording media, then storage capacity per unit volume is improved, but fluttering occurs more easily during high-speed rotation
Solution Approach 1:
The invention changes the material parameters of the Al alloy substrate by precisely controlling the composition ratios of Si (9.5-13.0 mass%), Mn (0.05-0.40 mass%), Zn (0.30-0.40 mass%), Sr (0.005-0.03 mass%), Cu (0.05-0.50 mass%), Mg (0.05-0.50 mass%), and Zr (0.03-0.30 mass%). This compositional parameter change increases the Young's modulus to 79 GPa or higher, enabling the substrate to maintain high rigidity even at reduced thickness (0.9 mm or less), thereby preventing fluttering during high-speed rotation while allowing increased storage capacity.
Solution Approach 2:
The invention creates a composite material system by combining multiple alloying elements (Si, Mn, Zn, Sr, Cu, Mg, Zr) in specific proportions within the Al alloy substrate. This composite approach leverages the synergistic effects of different elements: Si provides high rigidity, Mn and Zn enhance strength, Sr refines grain structure, and Zr improves mechanical properties. The resulting composite Al alloy achieves superior Young's modulus (79 GPa or higher) that prevents fluttering at reduced thickness.
2Reliability
If a glass substrate is used to reduce fluttering, then stability during rotation is improved, but toughness and ease of manufacture deteriorate compared to Al alloy substrates
Solution Approach 1:
The invention modifies the parameters of Al alloy substrates (which inherently have better toughness and manufacturability than glass) by precisely controlling the composition of multiple alloying elements. This parameter optimization increases the Young's modulus to 79 GPa or higher, achieving fluttering resistance comparable to or better than glass substrates, while retaining the superior toughness and ease of manufacture inherent to Al alloys.
3Reliability
If the Young's modulus is increased to reduce fluttering, then stability during rotation is improved, but the substrate becomes more difficult to machine
Solution Approach 1:
The invention optimizes the compositional parameters within specific ranges: Si (9.5-13.0 mass%), Mn (0.05-0.40 mass%), Zn (0.30-0.40 mass%), Sr (0.005-0.03 mass%), Cu (0.05-0.50 mass%), Mg (0.05-0.50 mass%), and Zr (0.03-0.30 mass%). These controlled parameter changes achieve the necessary Young's modulus (79 GPa or higher) for fluttering resistance while maintaining adequate machinability for mass production, balancing mechanical performance with manufacturing feasibility.
Data Source
AI summary
A base for a magnetic recording medium, includes a substrate made of an Al alloy and having a surface, and a film made of a NiP-based alloy and plated on the surface of the substrate. The film has a thickness of 7 μm or greater, and a ratio E/ρ is 29 or greater, where E [GPa] denotes the Young's modulus of the substrate, and ρ [g/cm3] denotes a density of the substrate.