## Mechanical properties of metal materials and heat treatment process

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- Issue Time
- 04-07-2020

**Mechanical properties of metal materials and heat treatment process （1）**

**"Four Elements" of Materials Science and Engineering**

**Exploring the relationship between these four elements covers all research in the fields of materials science and engineering.**

**It is the ability of engineering and technical personnel to be able to select appropriate materials according to the performance requirements and formulate corresponding processing techniques so that they will eventually have properties that meet the performance requirements.**

**Mechanical properties of materials**

The mechanical properties of the material refer to the behavior under the action of an applied load (external force) or a combination of load and environmental factors (temperature, medium, and loading rate).

Mechanical properties of metal | Commonly used mechanical performance index of metal |

Strength | Yield strength, tensile strength, fracture strength |

Plasticity | Percentage elongation,reduction of area, work-hardening exponential |

Springiness | elasticity modulus,elastic limit,proportional limit |

Hardness | BH, Vickers hardness,Rockwell hardness |

Toughness | static toughness, impact toughness, fracture toughness |

Fatigue | fatigue strength, fatigue life, fatigue notch sensitivity |

Stress corrosion | Stress corrosion critical stress field intensity factor,Stress corrosion cracking rate |

**Unidirectional static tensile stress of ****MS--- ****stress-strain curve**

**Stress-strain curve**

**1、 oa part， elastic deformation**

2、 abpart：elastic deformation +Plastic Deformation

3、 bcd part：the material has obvious plastic deformation,under the condition that the force is basically unchanged, the sample continues to elongate

4、 dB part：Elastic deformation + uniform plastic deformation

5、Point B, the phenomenon of neck shrinkage occurs, the local section of the sample obviously reduces the bearing capacity of the sample, the tensile force reaches the maximum value, and the sample is about to fracture.

2、 abpart：elastic deformation +Plastic Deformation

3、 bcd part：the material has obvious plastic deformation,under the condition that the force is basically unchanged, the sample continues to elongate

4、 dB part：Elastic deformation + uniform plastic deformation

5、Point B, the phenomenon of neck shrinkage occurs, the local section of the sample obviously reduces the bearing capacity of the sample, the tensile force reaches the maximum value, and the sample is about to fracture.

**Strength index**

**1. Strength refers to the ability of a material to resist plastic deformation and fracture。**

**Yield Strength**

**Δs= Fs/So**

**Fs: The tensile force that the sample bears when yielding (N)**

**So: Original cross-sectional area of the sample (mm)**

**Δs: The resistance of the material to obvious deformation is one of the main basis for the design and selection of tough materials.**

**2. Tensile strength**

**The maximum tensile stress that the specimen
withstands before breaking off reflects the resistance of the material
to the largest uniform deformation.**

**Δb=Fb/So**

**Δb is often used as a seat for brittle materials and as a basis for design.**