Aluminum Alloy Substrate for Magnetic Disks with Flutter Control
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Solution Overview
Problem
Current aluminum alloy substrates for magnetic disks face challenges in achieving high strength and reduced disk flutter, which leads to increased positioning errors and reading errors due to low rigidity and high-speed rotation, while existing solutions either require high precision and increased component costs or fail to effectively suppress disk flutter.
Innovation Solution
An aluminum alloy substrate with a specific composition including 0.4 to 3.0 mass % Fe and second phase particles with a longest diameter of 0.5 μm to 2.0 μm dispersed at 5000 particles/mm², combined with additional elements like Mn, Si, Ni, Cu, Mg, Cr, Zr, Zn, Ti, B, and V, to enhance strength and fluttering characteristics, and a production method involving continuous casting, cold rolling, and pressurization annealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the aluminum alloy substrate is thinned to increase storage capacity, then the storage density is improved, but the strength and rigidity of the substrate decrease
Solution Approach 1:
The patent changes the chemical composition parameters of the aluminum alloy by precisely controlling the content of Fe (0.05-3.0 mass%), Mn (0.05-3.0 mass%), Si (0.05-1.0 mass%), and other elements. This compositional parameter adjustment enables the substrate to achieve both high strength and good flutter characteristics even at reduced thickness, resolving the contradiction between storage capacity and substrate strength.
Solution Approach 2:
The patent creates a composite microstructure within the aluminum alloy by controlling the formation of second phase particles (Al-Fe-Si-Mn intermetallic compounds) with specific size ranges (0.5-2.0 μm longest diameter) and distribution densities (5000 particles/mm² or more). This composite structure provides reinforcement, enabling thin substrates to maintain high strength and resistance to disk flutter.
2Quantity of substance
If the aluminum alloy substrate is thinned and rotated at high speed, then the storage density is improved, but disk flutter increases causing positioning errors
Solution Approach 1:
The patent adjusts the alloy composition parameters, particularly increasing Fe content to 0.05-3.0 mass% and Mn to 0.05-3.0 mass%, which fundamentally changes the mechanical properties of the substrate. This parameter change reduces disk flutter by enhancing the substrate's rigidity and damping characteristics, thereby maintaining positioning accuracy even at high rotation speeds and reduced thickness.
Solution Approach 2:
The patent creates non-uniform distribution of second phase particles with specific size ranges (0.5-2.0 μm) and minimum density (5000 particles/mm²) throughout the substrate matrix. This local quality enhancement at the microstructural level provides targeted reinforcement that suppresses flutter vibrations while maintaining overall substrate thinness, resolving the contradiction between storage density and positioning reliability.
3Ease of manufacture
If conventional aluminum alloy compositions are used, then the substrate has good workability and plating properties, but the strength is insufficient for thin substrates
Solution Approach 1:
The patent modifies the conventional JIS 5086 alloy composition by adjusting Fe to 0.05-3.0 mass% (increased from 0.50 mass% or less), Mn to 0.05-3.0 mass% (increased from 0.20-0.70 mass%), and Si to 0.05-1.0 mass% (decreased from 0.40 mass% or less). These parameter changes enhance strength while the patent maintains workability by controlling the formation of second phase particles that do not adversely affect manufacturing processes.
Solution Approach 2:
The patent introduces a composite microstructure with second phase particles (Al-Fe-Si-Mn intermetallic compounds) dispersed in the aluminum matrix. This composite structure provides strength reinforcement without significantly compromising workability, as the particle size and distribution are controlled to avoid excessive brittleness or manufacturing difficulties, thus resolving the contradiction between strength and ease of manufacture.
4Strength
If Mg content is increased to improve strength, then the substrate strength is improved, but disk flutter suppression becomes insufficient
Solution Approach 1:
The patent changes the compositional parameters by limiting Mg to 0.05-1.0 mass% (decreased from 3.5-4.5 mass% in conventional alloys) while significantly increasing Fe to 0.05-3.0 mass% and Mn to 0.05-3.0 mass%. This parameter substitution achieves strength enhancement through Fe and Mn-based second phase particles rather than Mg, thereby improving both strength and flutter suppression characteristics simultaneously.
Solution Approach 2:
The patent creates specific local microstructural quality by controlling the size (0.5-2.0 μm longest diameter) and distribution density (5000 particles/mm² or more) of second phase particles formed from Fe and Mn. This local quality control provides effective flutter suppression through appropriately sized particles that dampen vibrations, while achieving strength through the same particulate reinforcement, thus resolving the contradiction between strength and flutter suppression.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides an aluminum alloy substrate with improved strength and reduced disk flutter, maintaining high strength and excellent fluttering characteristics, effectively addressing the positioning and reading errors associated with high-speed magnetic disk operations.
Implementation Method 1
a continuous casting step of continuously casting a cast sheet by using the aluminum alloy
Implementation Method 2
a cold-rolling step of cold-rolling the cast sheet
Implementation Method 3
the resultant is subjected to pressurization annealing in which the resultant is flattened by annealing the resultant while pressurizing both surfaces
Implementation Method 4
second phase particles having a longest diameter of 0.5 μm or more and less than 2.0 μm are dispersed at a distribution density of 5000 particles/mm2 or more
Data Source
AI summary
There are provided: an aluminum alloy substrate for a magnetic disk, the aluminum alloy substrate including an aluminum alloy including 0.4 to 3.0 mass % of Fe and the balance of Al and unavoidable impurities, in which second phase particles having a longest diameter of 0.5 μm or more and less than 2.0 μm are dispersed at a distribution density of 5000 particles/mm2 or more; a method for producing the same; and a magnetic disk using the aluminum alloy substrate for a magnetic disk.