Mg-Li Alloy Composition for Corrosion Resistance and Cold Workability
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Solution Overview
Problem
Magnesium-lithium alloys with high lithium content suffer from poor corrosion resistance and cold workability, limiting their practical application despite improved tensile strength.
Innovation Solution
A magnesium-lithium alloy with lithium content between 10.5% and 16.0% by mass, combined with specific ranges of aluminum and manganese, and controlled impurity concentrations, particularly reducing iron content to enhance corrosion resistance and cold workability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the lithium content is increased to more than 10.5% by mass to achieve a single β phase structure and improve cold workability, then the cold workability is improved, but the corrosion resistance is significantly deteriorated
Solution Approach 1:
The patent changes the chemical composition parameters by adding manganese (0.01-5.0 mass%) and controlling aluminum content (0.1-15.0 mass%) to modify the alloy's properties. This allows achieving both improved cold workability through single β phase structure and acceptable corrosion resistance through the synergistic effect of Mn and Al additions
Solution Approach 2:
The patent creates a composite alloy system by combining magnesium, lithium, manganese, and aluminum elements. The specific combination of Mg-Li-Mn-Al forms a composite material where Mn and Al work synergistically to improve corrosion resistance while Li provides the single β phase structure for good cold workability
2Strength
If the aluminum content is increased to improve tensile strength, then the tensile strength is increased, but the specific strength is slightly lowered and corrosion resistance is reduced compared to binary lithium-magnesium alloys
Solution Approach 1:
The patent optimizes the aluminum content parameter within a specific range (0.1-15.0 mass%) and combines it with manganese addition to achieve the desired balance between tensile strength and specific strength. The controlled Al content provides strength enhancement while the Mn addition compensates for any specific strength reduction
3Reliability
If the aluminum content is increased to improve corrosion resistance, then the corrosion resistance is improved, but it remains lower than that of binary lithium-magnesium alloys
Solution Approach 1:
The patent introduces manganese as an intermediary element that enhances the corrosion resistance provided by aluminum. Mn acts as a mediator that synergistically works with Al to improve corrosion protection, allowing the alloy to achieve better corrosion resistance than what Al alone could provide
Solution Approach 2:
The patent creates a multi-element composite alloy where Mn and Al work together synergistically. The combination of these elements produces a corrosion resistance level that exceeds the sum of their individual effects, allowing the alloy to overcome the limitation of binary Li-Mg systems
Data Source
AI summary
An Mg—Li alloy contains more than 10.50% by mass and not more than 16.00% by mass of Li, not less than 2.00% by mass and not more than 15.00% by mass of Al, not less than 0.03% by mass and less than 1.10% by mass of Mn, impurities, and the balance of Mg. The impurities contain Fe at a concentration of 15 ppm or less. The alloy may optionally contain M, which is at least one element selected from the group consisting Ca, Zn, Si, Y, and rare earth metal elements with atomic numbers of 57 to 71.