The Main Mechanical Properties Of Nickel-based Alloys

When using nickel-based alloy materials, we must first understand their mechanical properties to determine if they meet certain industrial requirements. These mechanical properties include: tensile strength (TS), yield strength (YS), elongation rate, and hardness, etc.

 

To obtain these data, a tensile test is required. The tensile test is used to determine the behavior of the material when subjected to axial tensile load. The equipment used for the tensile test is called a universal tensile machine.

 

 

Tensile strength (TS): The maximum stress that the material can withstand before breaking, it is the critical value at which the metal transitions from uniform plastic deformation to localized concentrated plastic deformation, and it is also the maximum load-bearing capacity of the metal under static tensile conditions. The symbol is Rm (the old national standard GB/T 228-1987 stipulates that the symbol for tensile strength is σb), and the unit is MPa.

 

Yield strength (YS): The critical stress value for the material to yield. Yield strength is the yield limit of the metal material when it undergoes the yield phenomenon, that is, the stress resisting minor plastic deformation. For metals without obvious yield phenomenon, the stress value causing 0.2% residual deformation is defined as its yield limit, called the conditional yield limit or yield strength. When a force greater than this limit acts on it, the part will undergo permanent deformation; when less than this, the part will return to its original state.

 

Elongation rate: The percentage of the total deformation ΔL of the specimen after tensile fracture to the original gauge length L: δ = ΔL/L × 100%. The high or low elongation rate indicates the ability of the material to absorb energy during the force application process and the plastic deformation ability of the material. The higher the elongation rate, the greater the permanent deformation that the material can withstand during the force application process, showing better plastic deformation ability, which is suitable for engineering scenarios requiring high toughness; while materials with a lower elongation rate exhibit brittleness and are prone to sudden fracture.

 

Hardness testing: Hardness is the ability of a material to resist local indentation on its surface. Common hardness testing methods include Brinell hardness (HB), Rockwell hardness (HR), and Vickers hardness (HC). Brinell hardness is suitable for plastic materials, Rockwell hardness is suitable for general metal materials, and Vickers hardness is suitable for thinner materials or small-area tests. A rough comparison among them can be made based on experience and test conditions.