ASTM/SAE publishs a reference
"Metals & Alloys in the Unified Numbering System".
It covers bout all the Conventions I ever heard of in the USA,
ASM, AMS, ASME, MIL, Federal, ASTM ACI, AISI, SAE, AWS & AA.
AMS is listed as a joint convention -SAE/Areospace Materials Specification.
Try http://www.sae.org/servlets/index