Age hardening push post

Hello All,

I need some help here to understand the processs to follow: I make
push post Butterflys by casting them in 18 K white and yellow gold.
The question is how do I get to strenghten them to get better grip
around the push post on every removal and not loosen the grip. Would
age hardening by heat treatment work??? If so how do I go about it ?
I use spring alloy for white and regular casting for yellow. I
understand that die struck backs do have more strength, but to get
them to the specs I need is difficult.

Khushroo Kotwal