That's very interesting.
I was taught the basics of hardening, tempering and annealing steel by my dad. One day in metalwork class at school, the subject of annealing copper came up. The teacher told us the heat and quench. I thought that this was pretty counter intuitive, but he demonstrated it and it actually worked and that's how I've done it ever since.
If I remember,( :drinkup ), I'm going to experiment with both methods at work tomorrow. I'll report on the results.
So I had a little play with this today.
My strictly unscientific experiment involved getting two copper strips and drilling a small hole in one end. I annealed them both, one by quenching and one by air-cooling. I then clamped them both to the edge of the bench, hung a piece of bent wire through the hole and started to hang weights (3/4" track nuts) on both pieces of wire to see which strip would bend first. And the results were........... wait for it.......
Taddaaaaaa. Both the same!
Within the grounds of error due to the crudity of my experiment, they both began to bend under the same amount of weight. I then straightened them out and repeated the test. This time the air cooled piece seemed a little less ductile then the quenched piece. I tried it a few more times and the air cooled piece was definitely work hardening the quicker of the two, but not much.
The only other difference was the quenched piece was clean and the air cooled piece had a layer of oxide on it.