Casting Heat Treatment

[Creigbm]

I am looking into have a part made out of A356 cast aluminum and was trying to figure out the difference between T6 and T61 (other than the obvious fact that T61 has a higher yield strength). Is T61 only used in permanent mold casting operations? I am using a sand cast and I saw on matweb that T61 was for permanent mold castings. If that is true, why? Thanks in advance for any help.

Regards,
Brian

 

[metengr]

Creigbm;
The following web site contains short technical articles on a variety of materials including information on cast aluminum alloys;

http://www.castingsource.com/tech_art_guide1.asp

The technical article of interest "A Guide to Aluminum Casting Aloys" describes differences between A 356 and 356 and describes the temper "T" nomenclature. It also describes differences between sand and permanent mold castings.

The A 356 aluminum alloy casting has T51, T6 and T61 tempers for permanent mold castings, indicating a slight variation in heat treatment to provide for mechanical property differences.

The sand cast version of A 356 has T51, T6 and T7 tempers- that once again refer to heat treatment variations.

The ASM Metals Handbook, Desk Edition, also has good reference material and is more in depth on cast aluminum alloys and their heat treatments.