Final answer:
The percentage increase in yield strength from strain hardening varies between aluminum, magnesium, and copper. Magnesium sees a higher increase due to its hexagonal structure while aluminum and copper, both with face-centered cubic structures, undergo moderate increases. The difference is due to the varying ease of deformation and dislocation movements in each metal's crystal structure.
Step-by-step explanation:
The percent increase in yield strength by strain hardening differs among commercially pure annealed metals like aluminum, magnesium, and copper. Strain hardening is a result of plastic deformation, which rearranges and entangles the atoms within a material's crystal structure, leading to an increase in strength. The extent of this strengthening effect depends on the metal's initial microstructure and how it can accommodate and lock dislocations—the linear defects around which plastic deformation occurs.
Aluminum, being a face-centered cubic (FCC) metal, has multiple slip systems that allow it to deform plastically before it work hardens. This property gives aluminum a moderate increase in yield strength during strain hardening. Magnesium, having a hexagonal close-packed (HCP) structure, has fewer slip systems available at room temperature; this makes it more difficult to deform, enabling a significantly higher increase in yield strength from strain hardening. Copper, another FCC metal like aluminum, also experiences an intermediate increase in yield strength with strain hardening, but the magnitude varies due to its innate ductility and larger stacking fault energy compared to aluminum.