The Influence Of Strong Magnetic Field And Different Temperature On The Carbide Precipitation And Dislocation Density Of High Chromium Steel During Tempering

Adjusting the alloy composition and improving the heat treatment scheme are important approaches to improve the steel material performance.The application of strong magnetic field to the material heat treatment is an emerging way of heat treatment,which have brought a significant influence to the steel material field.The purpose of this paper is to study the influence of strong magnetic field on carbide precipitation and dislocation density of high chromium steel at different tempering temperatures.In this paper,a type of high chromium heat-resistant steel was designed.The heat treatment was conducted with the superconducting high magnetic field equipment JMTD-12T100 and Gleeble 1500 simulator.After heat treatment,the tested samples were analyzed by OM?optical microscopy?,SEM?scanning electron microscopy?and TEM?transmission electron microscopy?.The carbide precipitation and dislocation density during tempering at 200°C,500°C,and 700°C with the presence of a 12-T strong magnetic field was carried out.The main results are as follows:1.The strong magnetic field increases the Ms point and promotes the transformation from austenite to martensite.During tempering at 500°C for 1 hour the presence of a 12-T strong magnetic field,the martensitic structure is more obvious with the dispersed dislocation lines.2.When tempered at 200°C,the strong magnetic field reduces the nucleation barrier?G^*,resulting in a higher nucleation rate,N,and an increase in the number of carbides precipitated.The magnetic field promotes the nucleation and precipitation of carbides,and the amount of carbides precipitated under a 12-T strong magnetic field is about 50%more than that without a magnetic field.3.The 12-T strong magnetic field reduces the energy required for nucleation of carbides and promotes the precipitation of carbides.When tempered at 500°C and700°C,carbides precipitated consists of mainly M₂₃C₆ and M₃C,and the area density of carbides is lower than that without magnetic field.The area density of carbides during tempering at 500°C with the presence of a 12-T magnetic field is 160%higher than that without a magnetic field.4.The 12-T strong magnetic field greatly promotes the precipitation of carbides.The dispersed distribution of carbides enhances the precipitation strengthening effect,making more movable dislocations into immovable dislocations due to the pinning effect of the precipitated particles.When tempered at 700°C with the presence of a12-T strong magnetic field,precipitated carbides increases by nearly two times,the dislocation density increases from 5.6×10¹⁴/m²?without magnetic field?to 11.8×10¹⁴/m²?with 12-T magnetic field?.5.The influence of a strong magnetic field on dislocation density increases with tempering temperature.When tempered at 700°C,the precipitation of carbides and the dislocation density are mostly affected.