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Chapter A.5

Selection Criteria for Aluminium Alloys5.1. Selection Criteria 735.2. Selecting an Alloy 74

5.2.1. Selecting an Alloy Series 745.2.2. Selecting a Metallurgical Temper 75

5.3. Principal Applications of Aluminium and Its Alloys 75

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Chapter A.5

Selection Criteria for Aluminium Alloys

The metallurgy of aluminium is highly developed and offers a vast choice of alloys amongthe eight series of alloys capable of satisfying highly varied requirements and applications.However, this advantage may sometimes create confusion among users, and may lead to anerroneous choice.

This often happens when an application is transposed from steel to aluminium.

Too often, only the mechanical properties are taken into account as the sole criterion of choice of the alloy, leaving out aspects such as corrosion resistance, which may well be anessential factor in certain applications.

In cases like this, one would almost certainly opt for 2017A or another alloy of the 2000series. However, if used in an aggressive environment, serious corrosion problems mayoccur.

It is, therefore, essential to take into account as many selection criteria as possible. Inthe above example, two approaches are possible. First, one can stick to 2017A, because theuse conditions require a high level of mechanical properties; in this case it will benecessary to provide for adequate protection against corrosion. Alternatively, a thoroughanalysis may lead to the conclusion that a lower level of mechanical properties isacceptable, and one may opt for another alloy in the 5000 or 6000 series of alloys, whichare more corrosion-resistant.

5.1. SELECTION CRITERIA

The selection criteria are very closely related to the application, as can be seen from thefollowing examples:

– in the construction industry, the criteria of durability of the surface appearance andcorrosion resistance are preponderant;

– for sheet-metal structures and fabricating, formability and ease of assembly are moreimportant;

– in mechanical engineering, the mechanical properties as well as suitability formachining are important;

– for heat exchangers, the metal’s thermal conductivity determines the efciency of theheat transfer, and resistance to corrosion is an important aspect.

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The requirements must, therefore, be dened very carefully. For example, it is difcultto talk about corrosion resistance without specifying the environment, or to discuss fatigue

strength without identifying stresses and load cycles: 106

, 107

.

5.2. SELECTING AN ALLOY

Whenever possible, the choice of an alloy should be based on the experience that has beengained, often over decades, with aluminium applications. First, this experience provides avaluable guidance for selection, once the decision to use aluminium has been taken.Second, experience forms the basis for the development of new applications, bycomparison with what is being done, or what has been done.

The choice of an alloy is a match between its properties, its engineering capabilities,and the conditions of service. The most common selection criteria are

– mechanical properties,– formability,– suitability for machining,– weldability,– suitability for anodising, and– corrosion resistance.

Certain alloys (or groups of alloys within the same series of alloys) specialise in certainapplications, either by tradition, or because they have been developed for a specic use.This is the case with alloys 2011, 2030 and 6262 for free machining, alloy 5005 for

construction, and alloy 3104 for canstock. However, these applications are not necessarilyexclusive.

5.2.1. Selecting an alloy series

One of the rst selection criteria must be in regard to the alloy series, because performanceand workability are quite different for strain-hardenable and age-hardenable alloys(Table A.5.1).

This is why it does not seem sensible to compare the properties of alloys in all eightseries in a single table. Both metallurgically and in terms of applications, there is nomuch similarity between 1050A or 8011 and 7049A. For this reason, the alloyseries 4000 and 8000, which are devoted to very specic applications, are not includedin Table A.5.1.

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Table A.5.2. Typical applications of aluminium and aluminium alloys

ApplicationsMain selection criteria

of usersAlloys commonlyselected by users Comments

Sheet-metal fabrication Forming, welding 1200, 1100, 1050A,3105, 3003, 3004,5049, 5052, 5454,5754, 5086, 5083,6082, 6061

Mechanical applications Mechanicalproperties,machinability

2618A, 2024, 2017A,2014, 2214, 2030,2011, 5086, 5083,6005A, 6082, 6061,6012, 6262, 7075,7049A

2030, 2011, 6012 and6262 are free,machining alloys

Construction of aircraftand spacecraft

Lightness, mechanicalproperties,formability,machinability,suitability forsurface treatments,corrosion resistance

2618A, 2024, 2014,2214, 2219, 7020,7075, 7175, 7475,7050, 7010

Commercial vehicles Forming, joining(welding),functionalities of semi-products,appearance,corrosion resistance

3003, 3004, 5052,5454, 5754, 5086,5083, 6005A, 6082

Shipbuilding Forming, welding,corrosion resistance

5754, 5086, 5083,6005A, 6082

Building Forming, joining,suitability foranodising andpainting,

corrosion resistance

1050A, 3105, 3003,3005, 5005, 5052,6060, 6005A, 6106

Pre-coated coil:1050A, 3105, 3003,3005, 5052; Pre-anodised coil: 5005

Outdoor installations,urban amenities

Forming, joining(welding),functionalities of semi-products,appearance,corrosion resistance

3003, 5052, 5086,5083, 6005A, 6082,6060, 6106

Tread plate: 3003,5754, 5086

Heat exchangers Thermal conductivity,forming, joining (brazing),corrosion resistance

1050A, 1100, 3003,3005, 6060, 6063,8011

For brazedexchangers:clad 3003 and 3005

Kitchen utensils Suitability fordeep drawing andsurface treatments

1200, 1050A, 8003,3004, 4006, 4007,5052, 5754

4006 and 4007 arealloys forenamelling

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