Alloy cast iron is an iron-carbon cast alloy with some other elements added. It is often made by melting some pig iron, furnace charge and other additives.In order to distinguish between steel and cast steel, cast iron is mainly defined by its carbon content, which generally has a minimum carbon content of 2.03%.Magnesium is added during the incubation process to reduce the sulfur content, whereas graphite is spherical rather than lamellar.And its mechanical performance is significantly improved, so it is widely used in various fields.

The properties of solid materials mainly depend on their crystal structures. Therefore, to properly select materials with satisfactory properties or to develop materials with better properties, it is necessary to be familiar with and even control the structures.Besides practical significance, it is of great theoretical significance to study the structure of solid materials.The type and characteristics of bonding bonds can be most directly and effectively determined by studying the structure of solid materials.Structural determination of solid materials has become an important research field in material science.

The high silicon molybdenum ductile iron and high nickel ductile iron were tested and analyzed by means of optical microscope, X-ray analysis, scanning electron microscope, energy spectrum analysis and microhardness test to understand their structure and composition.

The hardness tests of high silicon molybdenum nodular cast iron and high nickel nodular cast iron studied employ microhardness. In order to eliminate accidental factors in the test process, 3 samples are selected for each material, with 25 test points on each sample, 255 15HV for high silicon molybdenum nodular cast iron and 210 10HV for high nickel nodular cast iron.The hardness of high silicon molybdenum ductile iron is slightly higher than that of high nickel ductile iron.

This is mainly due to the ferrite matrix of high silicon molybdenum ductile iron and the austenitic matrix of high nickel ductile iron, at the same time, the carbon equivalent of high silicon molybdenum ductile iron is higher than that of high nickel ductile iron, resulting in more carbides in high silicon molybdenum ductile iron than that of high nickel ductile iron, resulting in the hardness of high silicon molybdenum ductile iron slightly higher than that of high nickel ductile iron.

The microstructures of high silicon molybdenum ductile iron and high nickel ductile iron were studied. The main conclusions are as follows:

1) The microstructure of high silicon molybdenum ductile iron consists of ferrite matrix, graphite, carbide of Mo and ferrosilicon compound.Graphite is uniform in size, generally distributed on grain boundaries or embedded in ferrite matrix; carbides are distributed at ferrite grain boundaries.

2) The microstructure of high nickel ductile iron consists of austenitic matrix, graphite, intermetallic compound FeN I3 and 2) the microstructure of high nickel ductile iron consists of austenitic matrix, graphite, intermetallic compound FeN I3 and 2) the microstructure of high nickel ductile iron consists of austenitic matrix, graphite and intermetallic compound FeN.I3 is composed of carbides of chromium or manganese; graphite is smaller than silicon-molybdenum nodular cast iron in size; carbides rich in Cr or Mn are distributed at grain boundaries, accompanied by intermetallic compound FeN i3.This is accompanied by intermetallic compound FeN i3.This is accompanied by intermetallic compound FeN i3.

3) Spheroidization of high nickel ductile iron decreases during smelting due to its saturation degree greater than 4.4.

4) The hardness of high silicon molybdenum ductile iron and high nickel ductile iron have little difference.