A blacksmith strikes a piece of metal with a hammer repeatedly. The metal slowly begins to glow as the temperature increases, and the metal becomes more malleable. Which changes on a microscopic level led to the visible changes in the properties of the metal?

Answer 1

When a blacksmith strikes a piece of metal with a hammer repeatedly, several microscopic changes occur in the metal that lead to the visible changes in its properties. These changes include:

1. Plastic deformation: The repeated hammer strikes cause the crystal structure of the metal to be distorted and rearranged. This plastic deformation of the metal's crystal lattice leads to changes in its shape and structure, making it more malleable.

2. Dislocation movement: The hammer strikes also cause the movement of defects called dislocations within the metal. Dislocations are line defects in the crystal structure, and their movement allows for the metal to deform without breaking. This movement of dislocations helps in redistributing stresses within the metal, making it more ductile.

3. Energy input: The mechanical energy from the hammer strikes gets converted into heat energy when the metal is deformed. This energy input heats up the metal, increasing its temperature. As the temperature rises, the kinetic energy of metal atoms also increases, leading to faster atomic vibrations and greater atomic mobility. The increased temperature makes the metal more malleable and facilitates further plastic deformation.

4. Grain refinement: The repeated deformation and heating cycles during the blacksmithing process can also lead to grain refinement in the metal. Grain boundaries are the interfaces between individual crystals or grains in a polycrystalline material. The plastic deformation and heating cause grain boundaries to become disrupted, and as the metal cools, new grains can form with smaller sizes, resulting in finer microstructure. This refined microstructure can contribute to improved mechanical properties of the metal, including increased strength and toughness.

Overall, these microscopic changes in the metal's crystal structure, dislocation movement, energy input, and grain refinement collectively lead to the visible changes observed in its properties, such as increased malleability and glowing due to elevated temperature.