5086 aluminium alloy is an aluminium–magnesium alloy, primarily alloyed with magnesium. It is not strengthened by heat treatment, instead becoming stronger due to strain hardening, or cold mechanical working of the material.
Since heat treatment doesn't strongly affect the strength, 5086 can be readily welded and retain most of its mechanical strength. The good results with welding and good corrosion properties in seawater make 5086 extremely popular for vessel gangways, building boat and yacht hulls.Boatbuilding with Aluminum, Stephen F. Pollard, 1993,
Basic properties 5086 has a density of , with a specific gravity of 2.66.
Melting point is .
Chemical properties The alloy composition of 5086 is:5086 Material properties at supplliersonline.com, accessed October 29, 2006 Chromium - 0.05%–0.25% by weight Copper - 0.1% maximum Iron - 0.5% maximum Magnesium - 3.5%–4.5% Manganese - 0.2%–0.7% Silicon - 0.4% maximum Titanium - 0.15% maximum Zinc - 0.25% maximum Others each 0.05% maximum Others total 0.15% maximum Remainder Aluminium
Mechanical properties The mechanical properties of 5086 vary significantly with hardening and temperature.
–O hardening Unhardened 5086 has a yield strength of and ultimate tensile strength of from . At cryogenic temperatures it is slightly stronger: at , yield of and ultimate tensile strength of ; above its strength is reduced.
Elongation, the strain before material failure, ranges from 46% at , 35% at , 32% at , 22% at , 30% at , 36% at , and increases above there.
–H32 hardening H32 strain hardened 5086, with properties measured at , has yield strength of , ultimate tensile strength of , and elongation of 6-12%.
–H34 hardening
–H112 hardening
–H116 hardening H116 strain hardened 5086, with properties measured at , has yield strength of , ultimate tensile strength of , and elongation of 12%.
Uses 5086 is the preferred hull material for small aluminium boats or larger yachts. Its high strength and good corrosion resistance make it an excellent match for yachting.
5086 has a tendency to undergo Stress corrosion cracking and is not used much in aircraft construction as a result.5xxx Plate information sheet at www.alcoa.com, accessed October 29, 2006
5086 has been used in vehicle armor, notably in the M113 Armored Personnel Carrier and M2 Bradley Infantry fighting vehicle.
Welding 5086 is often assembled using arc welding, typically MIG or TIG welding. The newer technique of Friction stir welding has also been successfully applied but is not in common use.
Arc welding reduces mechanical properties to no worse than –O hardening condition. For –H116 base material, measured at ambient temperature, yield strength decreases from to and ultimate strength from . The relatively low decrease in ultimate strength (about 10%) is extremely good performance for an aluminium alloy.
References
Further reading "Properties of Wrought Aluminum and Aluminum Alloys: 5086, Alclad 5086", Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Vol 2, ASM Handbook, ASM International, 1990, p. 93-4.
Aluminium alloy table