During the hot forging process of copper hot forgings, its microstructure undergoes a complex and critical evolution. In the initial stage of hot forging, as the temperature rises, copper atoms gain more energy and begin to vibrate actively. The atomic arrangement at the grain boundary is relatively chaotic and the energy is high, so atomic migration occurs first, resulting in the gradual blurring of the grain boundary and a tendency for the grain to grow. At the same time, crystal defects such as dislocations begin to move, merge and annihilate under the action of thermal activation, which to a certain extent reduces the distortion energy inside the crystal and makes the crystal structure tend to be regular.
As the forging deformation proceeds, the grains are elongated along the force direction under the action of external pressure. Dislocations proliferate and entangle with each other to form a cellular substructure. The formation of this substructure helps to coordinate the deformation of the grains, so that the material exhibits plastic flow on a macro scale. Moreover, due to the uneven deformation, a strain gradient is generated inside the grains, which causes the dislocation density distribution in different regions to change, further affecting the morphology and properties of the microstructure.
During the high temperature continuous stage of hot forging, the dynamic recovery process continues. Dislocations are rearranged by climbing, slipping, etc., forming low-energy dislocation walls and subgrain boundaries, and the subgrains are gradually refined and stabilized. Partial recrystallization may also occur. New undistorted grains nucleate and grow at the grain boundaries or subgrain boundaries of the deformed grains, consuming the surrounding deformed tissue, thereby reducing the energy inside the material.
The cooling process in the later stage of hot forging also has an important influence on the microstructure. If the cooling rate is fast, the copper atoms will not have time to diffuse, and a high supersaturated vacancy concentration and a certain dislocation density will be retained, which may form a non-equilibrium structure, which will increase the strength of the material but reduce the plasticity. Slow cooling gives atoms sufficient diffusion time, which helps to form a more balanced and stable microstructure with relatively uniform comprehensive performance. In-depth exploration of the microstructure evolution mechanism during copper hot forgings is of great significance for accurately controlling hot forging process parameters and optimizing copper hot forgings performance.
