Iron-nickel alloy 4J42 is an alloy material with excellent properties, and its chemical composition is mainly composed of iron and nickel. This alloy has a low coefficient of expansion and good thermal conductivity, and is widely used in electronics, communications, aerospace and other fields. The composition of the 1" specimen in phase 305 3 ( mass fraction is: face-centered cubic is 51 91, body-centered cubic is 47 48, l**es phase is 0 61, and the composite intermetallic compounds are mainly Fe, Nb: Ni. ni ， nb： fe。etc.;The composition of the 2" specimen in phase 302 7 ( mass fraction is: 53 02 in the face-centered cube, 46 01 in the body-centered cube, 0 96 in the l**es phase, and there are composite intermetallic compounds of the same type as the l" sample. 
The heat treatment system of 4J42 alloy The heat treatment system of 4J42 alloy includes two stages: solid solution and aging. Among them, solid solution is to heat the alloy to a certain temperature so that it reaches a uniform solid solution state within a certain period of time. The alloy is then rapidly cooled by water quenching or oil quenching to obtain a homogeneous solid solution structure. After that, the alloy is aged and heated to a certain temperature to form a stable precipitated phase, thereby improving the hardness and strength of the alloy. After relevant treatment, the sample was determined between 20 100, 2. The instruments are 0 8 x 10" a, 14 x 10" OC 2 x 10" After comparative analysis, although the linear expansion coefficient of NB alloying is increased compared with that of the reference sample, it is still required by referring to the relevant standards for 4J 36 ( D chamber wet. 00 1 5 10" 1) It is known that the alloy still has good low expansion properties after NB alloying. In addition, when NB accounts for 1 0 of the main raw material, the magnetostrictive effect has a greater impact on the performance than its own 0[. 4J42 Physical Properties Density: 814 g cm Melting Point: 1427-1450°C Coefficient of thermal expansion: 11 10 -6 K (20-100 °C) thermal conductivity: 128 W (m·k) (20°C) resistivity: 470 m (20°C) permeability: 1Although the 25 t (20°C) alloying element Nb belongs to the reduced and closed austenite region, it can be seen from the above XRD phase analysis results that when the Nb content in the alloyed sample is 0 28 and 0 44, respectively, the triple intensity diffraction peak matches the austenite diffraction in the standard PDF card library, which shows that the room temperature structure of the sample is mainly a single austenite, and the main phase is Fe. 。nb。, whose diffraction peaks are all in the crystal plane. 
Saturation magnetic induction intensity: 125 t (20°C) Yield Strength: 450 MPa (room temperature) Tensile strength: 550 MPa (room temperature) Hardness: HB 170-230 At room temperature, the microstructure of the specimen is austenitic and the crystal structure is face-centered cube. Specimens 1' and 2" than 0. The microstructure is more evenly distributed. Measure and calculate 4, 2. The average grain diameters of the observed surface of the specimen were 7 and 5 3 I xm, respectively, which showed that the grain size of the alloy was smaller after NB alloying. The alloying element NB has a higher melting point and tends to precipitate to form NBC-type carbides during the solidification process with decreasing temperature, and the elemental NB and its fine NBC particles act as the nucleation center to promote the heterogeneous nucleation and prevent the growth of grains, resulting in grain refinement. 
4J42 Chemical Composition Iron-Nickel Alloy The chemical composition of 4J42 is mainly composed of iron and nickel, of which the iron content is about 999% with a nickel content of about 008%-0.12%。In addition, it also contains small amounts of manganese, silicon, phosphorus and other elements. The composition ratio of this alloy has been carefully designed to give it excellent properties. The dislocations in the initially undeformed grains are distributed in the form of subgrain boundaries and dislocation nets, and there is a dislocation accumulation phenomenon at the grain boundaries, and with the further development of deformation, they will interact with the moving dislocations, which will cause the grains to become fragmented substructures.