i have z640 workstation with 48 gb ram ? if i doubles ram size can i get better performance ?

What you do mean by "better performance"?

You can get longer preview times by increasing RAM, but the preview rendering speed will stay the same (or nearly the same). If you use RenderGarden or such a like, you can run more parallel render jobs with more RAM which will decrease rendering time - but only for final renderings, preview rendering is not affected.

I did made such videos for several years. My machine was 64GB gaming hardware, with overclocked 4c/8t i7 and hardly used GTX 1080. If you are making explainers on a regulary basis, you should consider to get a new machine. Those Xeons are no benefit for AE. Too many cores with too less clock speed. Nothing AE is optimized for (sadly).

*Martin

Same old standard answer: Without knowing what kinds of projects you do and what they involve in terms of effects and features nobody can tell you if there would be any performance gains by updating parts of your hardware. The interactions of different features and settings are way to complex. and even though AE is a RAM-driven application, there simply are limits how far this will go. At some point the program simply won't use any more resources and increasing your memory won't achieve anything.

Mylenium