硬化的

例句：

1. 1. The frost hardened the ground into a crust.
   霜冻使地面变得坚硬如壳。
2. 2. The old tree's bark has hardened over time.
   老树的树皮随着时间变得坚硬。
3. 3.The metal was hardened by heating it in a furnace.
   金属通过在炉中加热而硬化。