Mechanical properties of metal materials and heat treatment process

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.

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.