Annealing is the effect due to which metals change their crystal structure during heating.
The brass samples were heated in an oven at 800 degrees Celsius and then allowed to cool in the oven overnight. The Rockwell Hardness Tester was used to measure the hardness of the brass samples, as seen in figure 1 below. First, the non-treated brass samples were tested. The sample was placed on the anvil, and the wheel was turned until the penetrator tip just barely made contact with the sample. To calibrate the tester, the wheel was turned further until the hands of the dial gauge lined up with the triangles on the gauge. A close up of the gauge can be seen below in figure 2. To begin testing, the lever was gently pushed forward, and the machine applied a load to the sample. After the lever had completely gone forward, it was pulled back. The hardness measurement could then be read on the dial gauge. This process was repeated the exact same way for the annealed samples.