Q: Why are some aluminium alloy designations followed by a letter T and some numbers whilst others have a letter H and some numbers?    
The H designations refer to alloys that can only be hardened or strengthened by cold work.  The numbers describe the extent of hardening achieved.
The T numbers are applied to alloys that respond to hardening or strengthening by heat treatment (solution treatment and age hardening).  The numbers refer specifically to the heat treatment condition.

Q: I need an aluminium alloy forging with a minimum 0.2% proof stress of 270MPa.

There are a number of options, but care is needed in selection depending on service environment:
• 2014A will easily give the properties suitably heat treated but may suffer from unacceptable corrosion is service.
• 6082, even suitably heat treated, will not achieve the 270MPa required but will give adequate corrosion behaviour in most environments. It may be better to re-design for the lower properties depending upon the service environment expected.

Q: I understand, and have used for years, the British Standard LM series designations for aluminium casting alloys. I believe that there are new designations now -  how do these relate to the LM numbers?
BS 1490, which specified the casting alloys under the LM designation has been replaced by BSEN 1706. A new system of numbers is now in place.  You should be aware that there are also designations under ISO 3522.
Copper alloys used to be specified under C numbers in the old BS system.  There are now new BSEN numbers.  

Q: How can I avoid corrosion problems with 2014A aluminium alloy?
There are a number of options:
•    apply a skin of pure aluminium
•    protective anodizing
•    use an alternative material with good corrosion properties.

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