Like many long time users, our custom material database file was set up back when Will Smith was Gettin Jiggy Wit It​.  It was eventually put into EPDM when Macklemore was Poppin' Tags and has been changed from time to time, but for the most part hasn't been given much thought.  Today I was using Assembly Visualization to find the heavy parts in a model and there was an aluminum part that looked svelte compared to its reported mass. I opened the part and the material is 6061-T6.  Editing the material and looking at 6061-T6 shows a density of 0.093 lb/in^3, which isn't quite right, but pretty close to the 0.098 reported by Matweb.  When I look at the mass properties for the part via Tools...Evaluate...Mass Properties, the density is reported as 0.146 lb/in^3, which is *way* off.  I looked through the file history in EPDM for the material database file and it turns out that when it was added to the vault, the density value was incorrect.  So, at some indeterminate time prior to that, the material properties were changed and it affected any parts made using that template.

The surprising thing to me that that it appears as though the material database acts much like a file template.  The value in the database when the material is applied is what is used from that point forward, despite any changes made to the database at a later date.  I didn't know that it worked this way, and I do not like that it works this way.  Is this documented somewhere?  Can anyone state a reason why this behavior is a good thing?