natural alloy

例句：

1. 1.The alloy is stronger and more durable than the pure metal.
   这种合金比纯金属更坚固耐用。
2. 2. In ancient times, gold was often used as a natural alloy for jewelry.
   在古代，黄金常被用作珠宝的自然合金。
3. 3. The engineers were experimenting with different natural alloys to improve the strength of the structure.
   工程师们正在尝试不同的自然合金来增强结构强度。