My reference book says copper/nickel alloys are annealed at between 800-1400F depending on the alloy. I would start at a dull red, let it go black and then quench. That is how I anneal brass and silver. I am told that there are charts showing the hardness curves by temperature for each alloy, but I don't have one of those. Maybe someone else does. One thing I did learn is that you can harden silver by overheating it. I learned that in a jewelry making class. I am assuming that could apply to a number of alloys.