Material Classification- Metal Materials

According to traditional classification, materials can be divided into metallic materials, inorganic non-metallic materials (ceramic materials), polymer materials and composite materials. Steel, gold, and silver are all metal materials. Inorganic non-metallic materials, including ceramics and glass, include oxides, inorganic salts, etc. in terms of cluster composition. Polymer materials are composed of organic macromolecules, such as fibers, rubber, resins, and plastics. Composite materials are composed of two or more materials in a certain way, and they are classified into many categories. According to the matrix, they can be divided into metal matrix, ceramic matrix, resin matrix, etc., or according to the reinforcement, they can be divided into fiber reinforced, particle Reinforced composite materials, etc., there are many types.

Understand metal materials and development trends. Metal materials refer to materials with metallic properties that are composed of metal elements or are mainly composed of metal elements. Including pure metals, alloys, intermetallic compounds and special metal materials.

Our understanding of metal materials should start from the following aspects:

1. Classification: Metal materials are usually divided into ferrous metals, non-ferrous metals and special metal materials.

① Ferrous metals are also called steel materials, including industrial pure iron containing more than 90% iron, cast iron containing 2% to 4% carbon, carbon steel containing less than 2% carbon, and structural steel, stainless steel, and heat-resistant steel for various purposes. Steel, high temperature alloy, precision alloy, etc. Generalized ferrous metals also include chromium, manganese and their alloys.

② Non-ferrous metals refer to all metals and their alloys except iron, chromium and manganese, which are usually divided into light metals, heavy metals, precious metals, semi-metals, rare metals and rare earth metals. The strength and hardness of non-ferrous alloys are generally higher than those of pure metals, and they have greater resistance and smaller temperature coefficient of resistance.

③Special metal materials include structural metal materials and functional metal materials for different uses. Among them are amorphous metal materials obtained through rapid condensation processes, as well as quasicrystalline, microcrystalline, nanocrystalline metal materials, etc.; there are also special functional alloys such as stealth, hydrogen resistance, superconductivity, shape memory, wear resistance, vibration reduction and damping, etc. , and metal matrix composite materials, etc.

Metal materials are divided into cast metals, deformed metals, injection formed metals, and powder metallurgy materials according to the production and molding process. Cast metal is formed through the casting process, mainly including cast steel, cast iron and cast non-ferrous metals and alloys.

Deformed metal is formed by pressure processing such as forging, rolling, stamping, etc., and its chemical composition is slightly different from the corresponding cast metal. Injection forming metal is made into parts and blanks with certain shapes and structural properties through the injection forming process.

The performance of metal materials can be divided into two types: process performance and usage performance.

2. Performance: 

In order to use metal materials more rationally and give full play to their role, it is necessary to master the performance (usability performance) that parts and components made of various metal materials should have under normal working conditions and their use during hot and cold processing. The performance that should be possessed (process performance). The performance of materials includes physical properties (such as specific gravity, melting point, electrical conductivity, thermal conductivity, thermal expansion, magnetism, etc.), chemical properties (durability, corrosion resistance, oxidation resistance), and mechanical properties. The process performance of materials refers to the material's ability to adapt to cold and hot processing methods.

3. Production process: 

In the production of metal materials, the metal is generally extracted and smelted first. Some metals need to be further refined and adjusted to the proper composition before being processed into products of various specifications and properties. To extract metals, steel usually uses pyrometallurgical processes, that is, converters, open-hearth furnaces, electric arc furnaces, induction furnaces, cupolas (iron-making), etc. are used for smelting and smelting; non-ferrous metals use both pyrometallurgical and hydrometallurgical processes; high-purity metals As well as metals requiring special properties, zone smelting, vacuum smelting and powder metallurgy processes are also used. After the metal material is smelted and its composition is adjusted, it is cast and shaped, or made into ingots and billets through casting and powder metallurgy forming processes, and then plastically processed into products of various shapes and specifications.

4. Development Trend:

The development of metal materials has moved away from pure metals and pure alloys. With the advancement of material design, process technology and performance testing, traditional metal materials have developed rapidly, and new high-performance metal materials have been continuously developed. High-temperature structures such as rapidly condensing amorphous and microcrystalline materials, aluminum-lithium alloys with high specific strength and high specific mode, ordered intermetallic compounds and mechanical alloying alloys, oxide dispersion strengthened alloys, directionally solidified columnar crystals and single crystal alloys Materials, metal matrix composite materials, and new functional metal materials such as shape memory alloys, neodymium iron boron permanent magnet alloys, and hydrogen storage alloys have been applied in various fields such as aerospace, energy, and electromechanics.