Al Alloy Substrate for HDD Base with High Young's Modulus
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Solution Overview
Problem
The existing Al alloy substrates used in magnetic recording media face challenges in reducing thickness while maintaining high Young's modulus, leading to fluttering issues during high-speed rotation, which affects data stability in hard disk drives.
Innovation Solution
An Al alloy substrate with specific compositions of Mg, Si, Zn, and Sr, along with a NiP-based alloy film, is used to achieve a high Young's modulus of 79 GPa or higher, ensuring a uniform plated film and improved machinability, allowing for a thinner substrate with a larger diameter and reduced fluttering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the Al alloy substrate is reduced to increase storage capacity, then the storage capacity per unit volume increases, but fluttering occurs during high-speed rotation affecting data stability
Solution Approach 1:
The invention changes the material parameters of the Al alloy substrate by optimizing the composition ratios of alloying elements (Mg: 2-10 mass%, Si: 3-17 mass%, Zn: 0.05-2 mass%, Sr: 0.001-1 mass%). This parameter optimization increases the Young's modulus of the substrate, enabling it to maintain high rigidity even at reduced thickness, thereby preventing fluttering during high-speed rotation while increasing storage capacity.
Solution Approach 2:
The invention uses a composite Al alloy substrate containing multiple alloying elements (Mg, Si, Zn, Sr) that work synergistically to enhance mechanical properties. The combination of these elements creates a composite material structure that achieves both high strength and high Young's modulus, allowing the substrate to be thinner without compromising rotational stability.
2Quantity of substance
If the thickness of the base is reduced to accommodate more media, then storage capacity increases, but the Young's modulus decreases leading to increased fluttering
Solution Approach 1:
The invention optimizes the compositional parameters of the Al alloy to achieve a Young's modulus of 79 GPa or higher. By precisely controlling the content ranges of Mg (2-10 mass%), Si (3-17 mass%), Zn (0.05-2 mass%), and Sr (0.001-1 mass%), the material achieves enhanced stiffness that compensates for the reduced thickness, maintaining structural integrity.
3Ease of manufacture
If conventional Al alloy compositions are used to maintain machinability, then ease of manufacture is maintained, but the Young's modulus is insufficient to prevent fluttering in thin substrates
Solution Approach 1:
The invention modifies the conventional Al alloy composition parameters within ranges that balance machinability and mechanical strength. The optimized composition (Mg: 2-10 mass%, Si: 3-17 mass%, Zn: 0.05-2 mass%, Sr: 0.001-1 mass%) maintains good machinability for mass production while achieving a Young's modulus of 79 GPa or higher, resolving the contradiction between ease of manufacture and structural performance.
Data Source
AI summary
A base for a magnetic recording medium includes, a substrate made of an Al alloy, and a film made of a NiP-based alloy and provided on the substrate. The Al alloy of the substrate includes Mg in a range of 0.2 mass % to 6 mass %, Si in a range of 3 mass % to 17 mass %, Zn in a range of 0.05 mass % to 2 mass %, and Sr in a range of 0.001 mass % to 1 mass %. An average grain diameter of Si grains in an alloy structure of the substrate is 2 μm or less. The film has a thickness of 10 μm or greater. The substrate has an outer diameter of 53 mm or greater, a thickness of 0.9 mm or less, and a Young's modulus of 79 GPa or higher.