Metals such as steel, aluminum and others, in different alloys and tempers, are used for manufacturing products in different shapes (sheets and plates, bars/rods, tubes, wires, etc.). They are widely encountered in aerospace, automotive and many other industrial sectors. Sourced from quality producers, most of them are offered as part of our own labelled (AVIATIONEU NEW ERA) product lines. They are available in pre-cut dimensions or cut-to-order, meeting different specifications and in different units of sale, (pieces or tons) depending on the order quantity and customer requirements. This article focuses on most popular steel and aluminum alloys used for manufacturing of products commonly demanded by our customers.
In selecting an aluminum or steel alloy, its composition and properties should be carefully considered. Some important measures of mechanical properties are ultimate strength, yield strength, shear strength, fatigue strength, as well as the modulus of elasticity and shear modulus. Shear and fatigue strength are measures of a material’s resistance to specific stressors. For shear strength, this means the resistance to shearing stresses, also known as “cutting” stresses. The fatigue strength is the measure of how resistant a material is to breaking under such fatigue. It is a valuable measure for alloys that appear in aerospace applications such as 2024 aluminum. Aircraft experience periodic stresses (such as from takeoff, landing, etc.), may not deform the alloy initially but, when repeatedly exposed, the alloy may weaken microscopically and then eventually macroscopically. Finally, the modulus of elasticity and shear modulus are parameters that display how “resilient” a given material is to deform. They give a good idea as to a material’s resistance to permanent deformation.
Aluminum Alloys
2000 Series Aluminum Alloys
The 2000 (*) series is an aluminum alloy family is a set of "hard alloys" with copper as the primary alloying element. 2000 series aluminum alloys typically contain between 2 to 10% copper, with smaller additions of other elements. The copper provides substantial increases in strength and facilitates precipitation hardening but can also reduce ductility and corrosion resistance. These alloys are known for high performance and excellent strength over a broad range of temperatures but can be the most challenging to weld. They find use in many industries, including the aerospace sector. An overview of 2000 series aluminum alloys is provided below.
(*) Aluminum alloys are named in accordance with a four-digit naming system developed by the US Aluminum Association to characterize a wide range of alloys on the basis of their main alloying elements.
Aluminum 2011 (A92011) is known as a free-machining alloy or 'FMA'. It displays a poor corrosion resistance (requiring anodizing for additional surface protection), poor weldability but has an excellent machinability and is suitable for use in the manufacture of highly complex and detailed parts.
Aluminum 2014/2014A (A24345) is a high strength aluminum, easily plated and can be hard anodized. The alloy is heat treatable, retaining its strength after heat treatment. It offers superior machinability and is used widely in the aerospace and defense sector in the manufacture of high strength components. Typically, 2014A aluminum alloy is found in T651 temper and produced in extruded bar or profile forms.
Aluminum 2017 (A92017) is a heat treatable wrought alloy with intermediate strength. It is stronger than aluminum 2011, but harder to machine. Workability is fair with ductility and formability better that aluminum 2014. Arc and resistance weldability of this alloy are satisfactory while corrosion resistance is fair.
Aluminum 2024 (A92024), the so-called aircraft aluminum, with copper as the primary alloying element (respective elemental percentages are 4.4% Cu, 1.5% Mg, and 0.6% Mn, nominally) is used in applications requiring high strength to weight ratio, as well as good fatigue resistance, weldability and average machinability. It comes in different tempers (O without heat treatment or T with heat treatment). Its density is 2.77g/cm3 (0.100 lb/in3), which is slightly higher than pure aluminum (2.7g/cm3, 0.098 lb/in3). 2024 aluminum alloy is machined very easily and has decent workability, allowing it to be both cut and extruded if need be. The addition of copper to this alloy makes 2024 one of the strongest aluminum alloys but greatly reduces its resistance to corrosion and therefore it is more prone to corrosion than most other aluminum alloys. For this reason a coating with a layer of corrosion-resistant metal (referred to as “galvanizing” or “cladding”) is often used. This coat is sometimes high purity aluminum or even another alloy, specified as CLAD or ALCLAD, and is most popular in clad sheet metal where the original alloy can be sandwiched between the cladding layers. Clad aluminum is so popular that a series of AlCLAD products have been developed and are widely used to give corrosion-weak alloys like 2024 the best of both worlds. This development makes 2024 aluminum especially useful because its strength can be implemented where the bare alloy would normally degrade.
5000 Series Aluminum Alloys
The 5000(*) series of aluminum alloys have magnesium as their primary alloying element. These alloys are readily weldable and used in a wide variety of applications including pressurized vessels, buildings and automotive. The 5000 series includes different grades such as the 5052, 5083, 5251 and 5754 discussed briefly below.
Aluminum 5052 is an aluminum alloy, with magnesium and chromium as the primary alloying elements. It is frequently used for general sheet metal work, heat exchangers, flooring panels, rivets and wires, chemical drums and other equipment, pressure vessels, treadplate, containers, and applications. Although It is non heat-treatable, it is the highest strength alloy of the more non-heat-treatable grades. Its resistance to fatigue is better than most grades of aluminum. Alloy 5052 has a good marine atmosphere corrosion resistance of saltwater and excellent workability. This alloy is comparable to the 6061 aluminum alloy (AL6061).
This alloy is comparable to the 6061 aluminum alloy. Similarities and differences are listed below:
Aluminum 5052: Non heat-treatable, Excellent weldability, High corrosion resistance, Smooth surface, Lightweight, High-tensile strength.
Aluminum 6061: Heat-treatable, Excellent machinability, Excellent corrosion resistance, Semi-smooth surface, Lightweight, High-tensile strength.
Aluminum 5083 alloy is well known for its exceptional performance in the most extreme environments. The alloy displays high resistance to both seawater and industrial chemical environments. It offers the highest strength of all the non-heat-treatable alloys but should not be used in temperatures above 65°C. The material combines excellent ductility with good formability and weldability and performs well in low-temperature service. Typical applications include pressure vessels, vehicle bodies, shipbuilding, rail cars, tipper trucks bodies, mine skips & cages.
Aluminum 5251 (formerly known as BS NS4) alloy is a non-heat-treatable rolled aluminum sheet designed for general sheet metal work where higher mechanical properties are required together with a degree of formability. Equivalent to EN AW 5251 H22 – AlMg2 grade. The higher strength and extra hardness of grade 5251 over pure aluminum give improved machinability properties. Machinability of the alloy is reasonable, though not as good when compared to the machining of heat-treated alloys. The alloy finds suitability in applications, including marine environments.
Aluminum 5754 alloy is a higher strength material than 5251 offering good workability and excellent weldability. It features superior resistance to both seawater and industrial chemical corrosion with applications in marine, oil & gas, chemical and nuclear sectors.
6000 Series Aluminum Alloys
The 6000 series is an aluminum alloy family with magnesium and silicon as their major alloying elements. The remarkable properties of 6000 alloys are their extrudability, excellent strength, and high corrosion resistance. 6000 series alloys can also be thermally treated to enhance their strength properties. Extrusion products in the 6000 series are perfect choices for structural and architectural applications. An overview of 6000 series aluminum alloys is provided below.
Aluminum 6005/6005A Alloys 6005 alloy contains greater amounts of silicon which reduces its melting point and enhances its extrudability. 6005A, on the other hand, contains higher amounts of chromium which reduces its susceptibility to stress corrosion and improves its toughness. 6005A also contains extra manganese, which increases its strength and extrudability. Producing thin-walled and intricate extrusion can be difficult with 6005, but it still has better extrudability than 6082. Both 6005 and 6005A possess excellent bending capabilities and a better mill surface finish than 6061. These two alloys can both be welded or brazed easily using commercial methods, but the heat from welding can diminish the strength of the alloy. Both 6005 and 6005A offer excellent corrosion resistance, finishing characteristics, and respond well to standard anodizing methods creating clear, clear and color dye, and hardcoat finishes. 6005 and 6005A are typically used for applications that require intricate extrusions such as tubing for furniture, components for railways and busses, pipe, portable ladders, and applications where much greater strength from 6063 is needed, as well as in some marine applications.
Aluminum 6061 alloy is the most commonly used aluminum alloy in the world and the most versatile and used alloy of all the other 6000 series alloys because of its high strength, good corrosion resistance, weldability, and machinability. Very popular for its characteristic toughness in medium- to high-strength applications. Like some of the other aluminum alloys, the 6061 aluminum alloy comes as annealed (O Temper) or in or tempered grades such as 6061-T4 and 6061-T6 or 6061-T651. When heat-treated, 6061 aluminum alloy is a great choice for general purpose uses and finds many applications in structural materials, electronics, chemical equipment but also in non-flight critical aircraft components and automotive components. 6061 is available in many forms, including extrusion sheets, and forgings.
Compared to 2024 Aluminum Alloy, the so-called aircraft aluminum, 2024 aluminum’s yield strength surpasses 6061 aluminum’s and should be generally selected if strength is a priority. Furthermore, the 2024 has a higher modulus of elasticity that 6061 aluminum, bearing more stress without permanently changing shape and therefore a better choice for forming applications. Compared to Aluminum 5052,the highest strength alloy of the more non-heat-treatable grades, the 6061 is heat-treatable and presents an excellent machinability, being one of the most popular machining alloys and therefore often preferred if machining procedures are necessary for a project.
Comparing 6061 to 6063 aluminum, 6061 aluminum and 6063 aluminum are both popular alloys used in extrusions for a variety of architectural, machinery, equipment, and consumer products. Both are similar in composition and mechanical properties and come in different tempers such as O (annealed), or tempered grades (e.g. T4 or T6). Their magnesium content provides increased strength, and silicon reduces their melting temperature. Their formability, weldability, corrosion resistance, and moderately high strength make these alloys quite versatile. However, even though they are from the same series of metals, there are some differences between them and factors that make each one suitable for different applications. 6061 aluminum is used in all kinds of applications ranging from electronics to welded assemblies. 6061 tubes, sheets, bars, and plates offer high- to moderate strength, excellent corrosion resistance, and superior machinability and weldability while 6063 aluminum tubes offer an excellent strength-to-weight ratio, superior corrosion resistance, and a fine appearance and finish. Typical applications of 6061 Aluminum alloy include:
Shipbuilding – sailboats, yachts, marine fittings, and hardware
Automotive – truck and bus bodies, wheels and various transportation end uses, brake and hydraulic pistons
Aerospace – aircraft structures and fittings
Rail – railway car components
Home and Business – furniture, awnings, moldings, and appliance fittings
Food Service – food and beverage cans
Miscellaneous – scuba tanks, pipe fittings, hinge pins, valve and valve parts, bike frames, fire ladders, bridge components, camera lens mounts, couplings, electrical fittings and connectors, magneto parks, structural framing, base plants, and gussets.
Aluminum 6063 alloy is a top choice for architectural materials because of its excellent response to extrusion; it is easily formed into complex shapes, including bars and tubing. 6063 aluminum bars and 6063 aluminum tubes offer a good surface finish for decorative finishes and resists corrosion more effectively than other 6000 series alloys due to the lack of copper in its elemental composition. While this alloy does not differ from 6061 aluminum in many ways, its lower strength and better corrosion resistance make 6063 aluminum a better choice for extrusion projects. With lower compositions of magnesium and silicon, this alloy is only half as strong as 6061 and suitable for use in applications where strength is not the fundamental consideration such as door and window frames, non-load-bearing posts, roofs, decorative structures, railings, furniture, parts for boats and motor vehicles, and electrical components such as conduit pipes, and tubes for irrigation systems. Highly corrosion resistant preventing environmental deterioration. Typical applications of 6063 Aluminum alloy include:
Architectural – trims, framework, brackets, and structural supports
Automotive – truck frames and trailers
Home goods – aluminum furniture and recreational equipment
General construction – pipes, tubing, stair rails, window frames, door frames, roofs, and signage
Aluminum 6082 alloy is generally known as “structural alloy” providing one of the highest strengths of all the 6000 series aluminum alloys replacing 6061 in some applications. It is a good alternative for engineers who don’t want to invest in the stronger 2000/7000 series aluminums and also enables the ability to extrude more complex shapes than those possible from 2000/7000 series alloys. 6082 is commonly known for machining, and it also features excellent weldability, cold formability, and corrosion resistance. Its high amount of manganese allows it to control its grain structure, resulting in a stronger alloy that is perfect for general purpose applications that require an extra degree in strength and toughness. One drawback is that it is harder to form thin-walled, complicated extrusion shapes using 6082 alloys versus other alloys in the 6000 series family. It is typically used in highly stressed applications such as bridges, towers, trusses, structural automotive, and structural marine applications.
7000 Series Aluminum Alloys
Commonly demanded alloys in this family include Aluminum 7050 and 7075.
Aluminum 7050 (known as a commercial aerospace alloy) is a heat-treatable aluminum alloy with zinc as the main alloying element, combining high mechanical strength, good stress corrosion cracking resistance and toughness at subzero temperatures. It features an excellent resistance to exfoliation corrosion. Particularly suited to heavy plate aerospace and other commercial and military applications, such as fuselage frames, bulkheads, wing skins and aircraft structures. Aluminum 7050 alloy can be hardened by precipitation heat treatment. It can be heat treated at 477°C (890°F) and cold worked using conventional methods. Welding should be avoided with Aluminum 7050, as the process weakens the alloy.
Aluminum 7075 is another "aircraft grade" aluminum with zinc and copper as its major alloying elements. Like aluminum alloy 2024, 7075 is a flexible and durable aluminum alloy extremely useful in highly stressed parts. Typically used in aerospace and defense, automotive, manufacturing and other applications requiring lighter weight and durable materials. This alloy features a high strength, low density (high strength-to-weight ratio), but also thermal properties and ability to be polished which makes 7075 a preferred choice for the mold making industry. AL7075 is available in various tempers, such as O (annealed) or tempered grades 7075-T6, and 7075-T651.
Steel Alloys
AISI/SAE(*) 1020 is a low hardenability and low tensile carbon steel alloy with Brinell hardness of 119 - 235 and tensile strength of 410 - 790 MPa. It features high machinability, high ductility, high strength, and good weldability. It is normally used in turned and polished or a cold drawn condition offering high machinability and can be used for drilling, turning, milling and tapping operations using suitable feeds, tool type and speeds. It can be welded by the most common welding processes. Due to its low carbon content, it is resistant to induction hardening or flame hardening. As an alternative to achieve a hardness value of more than Rc65, carburization or carbon nitriding can be performed, offering certain benefits over standard carburizing. This steel alloy is similar to SAE-AISI 4130 as they are both iron alloys. They have 98% of their alloy composition in common. They are commonly used in structural applications. Common uses of AISI 1020 steel include simple structural applications as well as manufacturing of axles, general engineering and machinery parts and components, shafts and camshafts, gudgeon pins, ratchets, light duty gears and spindles.
AISI/SAE(*) 4140 and 4130 low steel alloys have the same elemental composition, with common elements being carbon, molybdenum, chromium. They are popular steel materials due to properties such as toughness, high fatigue strength, and strength. Both steel variants do not have anti-rust properties. To make them stronger they need to be subjected to heat treatment such as annealing, cold working, etc. Steel alloy 4130 (ST4130), also known as Chromoly or Chrome Moly after the 2 key elements of its composition, chromium, and molybdenum, is a general-purpose alloy steel widely used by the aviation and motorsports industries due to its weldability, fabrication, and mild hardenability in all offered forms (tubes, bars, sheets and plates). Steel alloy 4140 (ST4140) is harder than normal steel remaining unbroken in heavy loading conditions. It is susceptible to rust although it is highly resistant to corrosion. 4140 steel also has good machinability but it has to be subjected to heat treatment. Often used for gears, crankshafts and other parts.
Grade 410 is a basic general-purpose harden able martensitic stainless steel alloy for highly stressed requirements, providing good corrosion resistance. Martensitic stainless steels are fabricated using techniques requiring final heat treatment. These grades are less resistant to corrosion when compared to those of austenitic. Their operating temperatures are often affected by their loss of strength at high temperatures, due to over-tempering and loss of ductility at sub-zero temperatures. Quenching and tempering can harden grade 410 steels while their corrosion resistance can be further enhanced by hardening, tempering and polishing. 410 is a very common grade used in many industries such as aerospace, power generation, and general industry. Generally used for applications requiring mild corrosion, heat resistance and high strength and ductility. Indicative examples include steam / gas turbine blades and buckets, bushings, valve components, fasteners, nuclear reactor control rod mechanisms, petrochemical equipment and machine parts.