Metallographic diagram of T8 (780℃, quenched)

Metallographic analysis of AISI 1070 steel after quenching at 780℃

The purpose of this metallographic analysis was to study the microstructure of AISI 1070 steel after quenching at 780°C (1436°F). The sample of AISI 1070 steel was annealed, then cut into thin slices. The thin slices were then mounted on a microscopic stage and polished with various grades of grinding paper. The polished thin sections were then examined under an optical microscope to obtain the microstructure images.

The microstructure of the AISI 1070 steel after quenching at 780°C (1436°F) was found to contain a large number of martensite laths. The martensite laths are long, thin needles or spindles of martensite that have been formed during quenching. There were also some very small carbide particles along the edges of the martensite laths. The carbide particles are likely the result of carbides forming along the grain boundaries during quenching.

The grain size of the AISI 1070 steel was large due to the quenching at 780°C (1436°F). The grains had a slightly dendritic structure, with an average grain size of 3.2μm. There were also some porosity present in the microstructure due to the quenching process. The presence of porosity can be seen as small voids between the grains.

The microstructure of the AISI 1070 steel after quenching at 780°C (1436°F) also contained some retained austenite which is the result of the quenching process. The retained austenite was found to be small in size and concentrated around the grain boundaries. This remained austenite is beneficial for the strength of the material because it increases the grain boundary strength.

In conclusion, the metallographic analysis of AISI 1070 steel revealed a strong martensite microstructure that contained a high percentage of martensite laths and some retained austenite. The grain size of the steel was large and there was some porosity present due to the quenching process. The presence of retained austenite is beneficial for the strength of the material due to its grain boundary strengthening properties.

A micrograph of the alloy T8 (780℃, Carburized) is presented. This particular alloy is composed of 43.9 %Cr, 19.6 %Si and 6.1 % Mn.

The structure of the alloy appears as a rounded plate-like grains of ferrite and pearlite, with a matrix of a mixture of ferrite and small amounts of carbides. This is characteristics of carburized alloys. Carburizing is a heat treatment process where carbon is introduced into the surface or a low alloy steel. This precipitates the formation of carbides at the surface, which provide high wear resistance and strength.

The pearlite and ferrite present in the micrograph are a result of the heat treatment. Pearlite is formed by the diffusion of carbon through the steel, which precipitates at the grain boundaries. Ferrite, on the other hand, is formed when excess carbon is dissolved in the surrounding iron crystal.

The grain boundaries appear well defined, with a thin layer of pearlite marking the interface. The plate-like grains also show very little deformation, indicating good toughness and resistance to deformation.

The microstructure of this alloy exhibits high strength while maintaining ductility and wear resistance. These properties make T8 (780℃, Carburized) an excellent choice for demanding applications, especially in indirect contact with materials like food, water, and molten aluminum.