合金，是由两种或两种以上的金属与金属或非金属经一定方法所合成的具有金属特性的物质。
制作合成编辑
常将两种或两种以上的金属元素或以金属为基添加其他非金属元素通过合金化工艺（熔炼、机械合金化、烧结、气相沉积等等）而形成的具有金属特性的金属材料叫做合金。但合金可能只含有一种金属元素，如钢。（钢，是对含碳量质量百分比介于0.02%至2.00%之间的铁合金的统称）
这里我们需要注意，合金不是一般概念上的混合物，甚至可以是纯净物，如单一相的金属互化物合金，所添加合金元素可以形成固溶体、化合物，并产生吸热或放热反应，从而改变金属基体的性质。
合金的生成常会改善元素单质的性质，例如，钢的强度大于其主要组成元素铁。合金的物理性质，例如密度、反应性、杨氏模量、导电性和导热性可能与合金的组成元素尚有类似之处，合金的抗拉强度和抗剪强度却通常与组成元素的性质有很大不同。这是由于合金与单质中的原子排列有很大差异。
少量的某种元素可能会对合金的性质造成很大的影响。例如，铁磁性合金中的杂质会使合金的性质发生变化。
不同于纯净金属的是，多数合金没有固定的熔点，温度处在熔化温度范围间时，混合物为固液并存状态。可以说，合金的熔点比组分金属低。参见低共熔混合物。常见的合金中，黄铜是由铜和锌的合金；青铜是锡和铜的合金，用于雕象、装饰品和教堂钟。一些国家的货币都会使用合金（如镍合金）。
一般通过熔合成均匀液体和凝固而得。根据组成元素的数目，可分为二元合金、三元合金和多元合金。
人类生产合金是从制作青铜器开始，世界上Zui早生产合金的是古巴比伦人，6000年前古巴比伦人已开始提炼青铜(红铜与锡的合金)。中国也是世界上Zui早研究和生产合金的国家之一，在商朝（距今3000多年前）青铜（铜锡合金）工艺就已非常发达；公元前6世纪左右（春秋晚期）已锻打（还进行过热处理）出锋利的剑。
合金是宏观均匀，含有金属元素的多元化学物质，一般具有金属特性.任何元素均可采用作合金元素，但大量加入的仍是金属.组成合金的Zui基本的、独立的物质称组元，或简称为元.由两个组元组成的合金称为二元合金，由三个组元组成的合金称为三元合金，由三个以上组元组成的合金称为多元合金.固态下，合金可能呈单相亦可能呈复相的混合物;可能呈晶态、亦可能呈现准晶状态或非晶状态.晶态合金中依其组成元素的原子半径、负电性以及电子浓度等等差异情况不同，可能出现的相有保持与基底纯元素相同结构的固溶体(solidsolution)以及不和任何组成元素结构相同的中间相(inter-mediatephases).中间相包括正常价化合物、电子化合物、laves相、σ相、间隙相和复杂结构的间隙式化合物等等.合金在平衡状态下可能出现的相可以从相平衡图得知.[2]
合金中组成相的结构和性质对合金的性能起决定性的作用.合金组织的变化即合金中相的相对数量、各相的晶粒大小，形状和分布的变化，对合金的性能也发生很大的影响.利用各种元素的结合以形成各种不同的合金相，再经过合适的处理可能满足各种不同的性能要求.[2]
高分子化学中现也借用合金一词，它指在一定条件下把聚合物或共聚物与另一种聚合物或弹性物掺合而成的复合材料，如苯乙烯-丙稀腈共聚物树脂与丁二烯-丙稀腈橡胶掺合.[2]
Alloys are substances with metallic properties synthesized bytwo or more metals and metals or non-metals by a certainmethod.
Making Composite Editors
Metallic materials with metal properties are often formed byalloying processes (smelting, mechanical alloying, sintering, vapordeposition, etc.) by adding two or more metal elements or othernon-metallic elements on the base of metals. But alloys may containonly one metal element, such as steel. (Steel is a general term forferroalloys with a mass percentage of carbon between 0.02% and2.00%)
Here we need to note that alloys are not general conceptualmixtures, or even pure substances, such as single-phase metalintermetallic alloys. Adding alloying elements can form solidsolutions, compounds, and produce endothermic or exothermicreactions, thus changing the properties of the metal matrix.
The formation of alloys often improves the properties ofelemental elements. For example, the strength of steel is greaterthan that of its main constituent element, iron. The physicalproperties of alloys, such as density, reactivity, Young's modulus,electrical conductivity and thermal conductivity, may be similar tothe constituent elements of alloys, but the tensile strength andshear strength of alloys are usually quite different from those ofthe constituent elements. This is due to the great difference inatomic arrangement between alloys and elementary substances
A small amount of some element may have a great influence on theproperties of the alloy. For example, impurities in ferromagneticalloys can change the properties of alloys.
Unlike pure metals, most alloys have no fixed melting point.When the temperature is in the range of melting temperature, themixture is in the state of solid-liquid coexistence. Therefore, itcan be said that the melting point of the alloy is lower than thatof the component metal. See eutectic mixtures. Among the commonalloys, brass is an alloy of copper and zinc; bronze is an alloy oftin and copper, used for statues, ornaments and church bells. Somecountries use alloys (such as nickel alloys) in theircurrencies.
It is usually obtained by melting homogeneous liquids andsolidification. According to the number of elements, it can bedivided into binary alloys, ternary alloys and multicomponentalloys.
Mankind began to produce alloys from bronzes. The first peopleto produce alloys in the world were the Babylonians. Six thousandyears ago, the Babylonians began to extract bronze (the alloy ofbronze and tin). China was also one of the earliest countries inthe world to research and produce alloys, and the bronze(copper-tin alloy) technology was very developed in the ShangDynasty (more than 3000 years ago); around the 6th century B.C.(late Spring and Autumn) it had forged (and heat-treated) sharpswords.