Materials are a milestone in the progress of human society

Materials are the foundation and forerunner of economic and social development

The bonding bonds of simple metals are metallic bonds

Ceramic materials are mainly based on ionic bonds

Atoms in macromolecules are held together by strong covalent bonds

Bonding is very complex

Emphasis on mechanical properties

Emphasis on physical and chemical properties

Excessive elastic deformation → Insufficient stiffness is the root cause of excessive elastic deformation of parts (ceramics have the highest elastic modulus)

Excessive plastic deformation → low yield strength is the root cause of excessive plastic deformation of parts

There is no obvious difference between the two

There are three processes: crack initiation, propagation, and final fracture.

Classification of fractures

Fracture of parts under static and impact loads

Fatigue fracture of parts under alternating loads

Fracture of parts under static and impact loads

Classification

wear and tear

corrosion

Thermal effects: heat absorption, heat transfer and expansion

Dielectricity

Reversible (elasticity) and irreversible (plasticity)

The indicators that measure toughness include impact toughness and fracture toughness.

Oxide raw materials (alumina, magnesium oxide, spinel, mullite, etc.)

non-oxide raw materials

PVD method (physical vapor deposition method)

CVD method (chemical vapor deposition method)

Melting method, solution method, interfacial method, liquid phase precipitation method, sol-gel method, hydrothermal method (high temperature and high pressure or high temperature and normal pressure), spray method, solution growth method,

High temperature sintering method

powder metallurgy

solid phase polycondensation method

Self-propagating high temperature synthesis method

free flow molding

Forced flow forming

Forced plastic molding

Other molding

Metal casting is formed by taking advantage of the flowability of the material

Flowability and plastic deformability

Casting

plastic molding

Connection molding

macro level

microscopic level

micro level

1. Due to the strong binding force of ionic bonds, ionic crystals generally have higher melting points, boiling points and higher hardness.

2. Typical ionic crystals are colorless and transparent

3. Ionic crystals are good insulators

directional and saturating

The molecular crystal hardness is very low, and the melting and boiling points are also very low.

directional and saturating

A kind of crystal between crystal and amorphous

It is a solid in which the internal particle three-dimensional space does not display a periodic repeating arrangement. It has short-range orderly arrangement but does not have long-range orderly arrangement.

It refers to a solid formed by the regular arrangement of atoms or atomic groups, ions or molecules in a three-dimensional space in a periodic and repeated manner.

structural basis

crystal defects