Al-Mg Alloy Pipe with Zn Surface Layer for Strength
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Solution Overview
Problem
5000 series aluminum alloy pipes face challenges in achieving both good extrusion properties and increased strength, as high Mg content required for strength increases extrusion pressure, making porthole extrusion difficult.
Innovation Solution
A Zn-containing layer is formed on an extruded Al—Mg series alloy pipe by spraying Zn and subjecting it to diffusing heat treatment, increasing the strength of the pipe without raising Mg content, thereby improving extrusion properties and hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Mg content is increased to achieve higher strength, then strength is improved, but extrusion pressure increases and porthole extrusion becomes difficult
Solution Approach 1:
The patent applies local quality by creating a Zn-containing layer specifically at the outer surface portion of the pipe, rather than uniformly distributing Zn throughout the entire pipe cross-section. This localized Zn enrichment provides strength enhancement where needed (at the surface) without interfering with the extrusion process in the bulk material. The Zn-containing layer is formed through surface treatment followed by diffusion, concentrating the strengthening element at the surface while maintaining good extrusion properties in the base material.
Solution Approach 2:
The patent applies preliminary action by forming the Zn-containing layer on the extruded pipe surface before final use. The process sequence is: (1) extrude the Al-Mg alloy pipe with controlled composition for good processability, (2) form a Zn-containing layer on the surface through spraying or alodining, and (3) perform diffusion treatment to enhance strength. This preliminary surface treatment allows the base material to be optimized for extrusion while adding strength properties afterward.
2Strength
If Mg content is increased to achieve higher strength, then strength is improved, but hardness increases and processability deteriorates
Solution Approach 1:
The patent applies local quality by concentrating the Zn-based strengthening mechanism at the outer surface portion of the pipe. The base Al-Mg alloy maintains its original composition and good processability, while the surface layer provides enhanced strength and hardness through Zn diffusion and precipitate formation. This spatial separation of functions allows the bulk material to remain soft and workable while the surface provides strength.
Solution Approach 2:
The patent creates a composite structure consisting of the base Al-Mg alloy pipe and a Zn-containing surface layer. This composite structure combines the advantages of both materials: the Al-Mg base provides good extrusion properties and formability, while the Zn-containing surface layer provides enhanced strength and hardness. The composite structure is achieved through surface coating followed by diffusion, creating a metallurgical bond between the two material systems.
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 process enhances the strength of the aluminum alloy pipe by forming a Zn-containing layer with high Vickers hardness, improving extrusion properties and corrosion resistance without compromising productivity.
Implementation Method 1
Sn is sprayed to the extruded pipe with a predefined Zn deposition amount in a predefined area
Implementation Method 2
the obtained extruded pipe is subjected to diffusing heat treatment to provide the Zn-containing layer, Zn being diffused in the Al—Mg series alloy
Implementation Method 3
the obtained extruded pipe is subjected to diffusing heat treatment to provide the Zn-containing layer
Implementation Method 4
Zn diffused in the Al—Mg series alloy and solid solution Mg in the mother phase produce fine MgZn2 precipitate
Implementation Method 5
Zn diffused in the Al—Mg series alloy and solid solution Mg in the mother phase produce fine MgZn2 precipitate
Data Source
AI summary
An aluminum alloy pipe includes a pipe body portion made of an Al—Mg series alloy that includes Mg at a concentration equal to or higher than 0.7 mass % and lower than 2.5 mass % and Ti at a concentration higher than 0 mass % and equal to or lower than 0.15 mass %, with the balance being Al and unavoidable impurities, and a Zn-containing layer being outside the pipe body portion and including Zn being diffused in the Al—Mg series alloy at a concentration equal to or higher than 0.1 mass %.