Ax 2012 Database Entity Relationship Diagrams

The "AxErd" website hosts entity relationship (ER) diagrams for core tables of the application modules in Microsoft Dynamics AX 2012 R2. You can use the site to quickly list all the foreign key relationships for a table, involving both its child and parent tables. You can also use the site to determine which module a table is in, and which tables are in a module.
http://www.microsoft.com/dynamics/ax/erd/ax2012r2/

Example:

ERD: Accounts receivable, M2 CustTrans

http://www.microsoft.com/dynamics/ax/erd/ax2012r2/Erd-One-AcctRecv-M2-CustTrans-vsd.png