📚 Metal Alloys | 金属合金
When you think of metals, you might imagine pure elements such as iron, copper or gold. In real life, however, most metal objects are made from alloys. An alloy is a mixture of a metal with one or more other elements. This article explains what alloys are, why they are useful, and how they are different from pure metals.
提到金属时，你可能会想到铁、铜或金等纯元素。然而在现实生活中，大多数金属制品都是由合金制成的。合金是一种金属与一种或多种其他元素组成的混合物。本文将解释合金是什么、为什么它们很有用，以及它们与纯金属有何不同。
1. What Is an Alloy? | 什么是合金？
An alloy is a mixture of two or more elements, where at least one element is a metal. The elements are melted together and then allowed to cool into a solid. Alloys are mixtures, not chemical compounds, because the atoms are not chemically bonded in a fixed ratio.
合金是由两种或两种以上元素组成的混合物，其中至少一种元素是金属。这些元素先被一起熔化，然后冷却成固体。合金是混合物，不是化合物，因为原子之间没有按固定比例发生化学键合。
For example, brass is made from copper and zinc. You can change the amounts of copper and zinc to make different types of brass with slightly different properties.
例如，黄铜由铜和锌制成。你可以改变铜和锌的比例，制造出性质略有不同的黄铜。
Because alloys contain atoms of different sizes, their structure is less regular than a pure metal. This small difference has a big effect on strength.
由于合金含有大小不同的原子，其结构不如纯金属规则。这个微小的差别对强度有很大的影响。
2. Why Are Alloys Stronger Than Pure Metals? | 为什么合金比纯金属更坚固？
In a pure metal, atoms are arranged in regular layers. When a force is applied, these layers can slide over each other easily. This is why pure metals are often soft and can be bent or hammered into shape.
在纯金属中，原子排列成规则的层状结构。施加力时，这些原子层很容易相互滑动。这就是纯金属通常较软、可以被弯曲或锤打成形的缘故。
In an alloy, atoms of different sizes are mixed into the layers. The larger and smaller atoms disturb the neat arrangement, like mixing large and small balls in a box. The layers can no longer slide over each other as easily, so the alloy is harder and stronger.
在合金中，大小不同的原子混入原子层。较大的原子和较小的原子打乱了整齐排列，就像把大小不同的球混放在一个盒子里。原子层不再容易相互滑动，因此合金更硬、更坚固。
This explains why pure copper is too soft for many jobs, but bronze and brass, which are alloys of copper, are strong enough to make tools and machine parts.
这就解释了为什么纯铜在很多用途上太软，而青铜和黄铜等铜合金却足够坚固，可以用来制造工具和机器零件。
3. Common Alloys and Their Metals | 常见合金及其组成金属
The table below shows some common alloys, the metals they contain, and typical uses.
下表列出了一些常见合金、它们所含的金属以及典型用途。
| Alloy | Main metals | Typical use |
|---|---|---|
| Steel | Iron + carbon | Buildings, cars, bridges |
| Stainless steel | Iron + chromium + nickel | Cutlery, sinks, medical tools |
| Bronze | Copper + tin | Statues, medals, bearings |
| Brass | Copper + zinc | Musical instruments, taps |
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