one Q about heat treatment of gold alloy

[brittleness]

dental type iii and iv gold-copper alloys should be hardened by

1 quenching immediately after casting
2 quenching after recrystallization
3 heating to 700C for 10 minutes and quenching
4 heating to 350C for 15-30 minutes and slow cooling

the answer is the last two. why? and in what text book can i find related explanation?

please explain ,thanks 😕

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