The Effect Of Deformation Process On The Microstructure And Precipitated Phases Of Copper-containing Steel During Aging Evolutionary Influence

Copper-containing high-strength low-alloy steel has comprehensive properties such as high strength,good toughness,and excellent weldability.Therefore,it is widely used in aerospace and navigation,pipelines,medical equipment,high-pressure vessels,heavy machinery,nuclear industry,etc.For copper-containing high-strength low-alloy steel,its composition design adopts ultra-low carbon to obtain good welding performance.At the same time,it uses thermomechanical control and heat treatment process to use copper to form nano-scale secondphase particles and alloy elements to refine grain growth.The role of solid solution strengthening,fine-grain strengthening,phase change strengthening,precipitation strengthening,dislocation strengthening and other strengthening mechanisms are used to obtain copper-containing advanced high-strength steels with excellent performance.Therefore,it has important theoretical and practical significance to explore the precipitation law of copper in the aging process and the mechanism of strengthening the effect.The precipitation strengthening of Cu atoms in copper-containing steel has an important influence on the matrix structure and properties.The strengthening effect depends on the size,number density and distribution of the precipitated phases.In addition,changes in the elemental composition of the precipitated phases are observed in the process of structural evolution.In the early stage of aging,the main components of the precipitated phases of Ni,Mn,and Al,although these elements are The effect of segregation on the nano-precipitated phase is not clear,but it is certain that in addition to copper,there are Ni,Mn,Al,etc.in copper precipitation strengthened steels.Ni is an important component of most copper-containing steels and can be effective.Prevent hot brittleness during thermal deformation.In this paper,a 25 Kg vacuum induction furnace was used to smelt copper-containing steel for experimental steel smelting,solution treatment was carried out at 900℃,followed by warm deformation rolling,and finally isothermal aging at 500℃,and the hardness test of the experimental steel was carried out.The hardness test results showed that during the aging process,the hardness values of the 1# and 2# samples increased significantly,and the peak value appeared at about 60 minutes.In addition,the peak plateau of 1# is shorter than that of 2# sample.The overall trend of 1# sample is first rising and then falling,while the 2# trend is first rising and then tending to be flat.On the other hand,the microstructure,morphology,and the size,distribution,and shape of the nano-scale precipitated phases of the sample are observed and analyzed using a Zeiskin microscope(OM),scanning electron microscope(SEM),etc.The results of microstructure and precipitated phase analysis showed that after aging treatment,the structure of the experimental steel showed polygonal ferrite and lath martensite.With the extension of aging time,the copper-rich precipitated phase dispersed and precipitated,showing a BCC structure.The matrix has a coherent structure,and the precipitated phase nucleates at the grain boundary,the size is about1.5nm～20nm,and with the extension of the effective time,the shape gradually changes from a round shape to an ellipse shape.At the same time,the influence of rolling deformation process on the evolution of microstructure and the law of desolventization was studied.the results show that rolling deformation causes a large number of dislocation density,which provides nucleation position and driving force for the precipitation of copper atoms in the process of desolventization,increases the nucleation rate,promotes the precipitation of copper-rich,and the particles are fine and dispersed,and the strengthening effect is significant,The microstructure is smaller,the aging time is prolonged,the growth of the precipitated particles is not obvious,and the dispersion is kept small.The above research on the influence factors of the precipitation process of coppercontaining steel will help to understand its strengthening behavior,so as to provide a theoretical and experimental basis for the development and application of a new generation of copper-alloyed steel.