(a)何種排列的方式會有比較高的硬度?為什麼?

5. To improve the physical and chemical properties of metal materials, it is common to introduce heteroatoms into the parent material to form a solid solution during metallurgy. Please describe what types of solid solutions that heteroatoms can form, and describe what factors affect the solubility of these heteroatoms in the solid solutions. [10分]