Effect Of Ni And Al Addition On Ageing Behavior And Microstructure Evolution Of Fe-Cu Alloy

Due to its excellent comprehensive performance,copper-containing steel has continuously expanded its application fields and is widely used in various industries such as construction materials,high-pressure transmission pipelines,automobile industry,high-pressure containers,and ships.In the composition design process of copper-containing steel,in order to improve the strength of the steel,the transition depends on the amount of carbon content,thereby greatly reducing the carbon content.,Such as high strength,high toughness,and excellent welding performance and mechanical processing performance.In this paper,Fe-Cu alloy with Ni and Al added is selected as the material.After aging at 900℃ for different time,the mechanical properties test,optical microscope(OM),scanning electron microscope(SEM)and transmission electron microscope(TEM)are adopted.By means of characterization and other means,the effects of Ni and Al on the structure evolution of the Fe-Cu alloy aging process were studied,and the mechanism of its effect on the strengthening of the Fe-Cu alloy was discussed.The following conclusions were obtained:During the aging process,the Fe-Cu alloy structure is always polygonal ferrite;after adding Ni and Al,it becomes a lath martensite structure.The Ni and Al elements improve the hardenability of the steel and refine the lath martensite.Slat bundle size.As the aging time increases,the lath structure of martensite begins to decompose and gradually transforms into polygonal ferrite.The addition of Ni and Al makes the hardness of the alloy significantly increase.During the aging process,the microhardness of the material increases first and then decreases with the increase of the aging time,and both reach the peak of the hardness at 32 minutes.In the under-aging period(t< 32min),the precipitate is now in the nucleation stage.At this stage,the size of the precipitate gradually decreases with the aging,and the number density increases significantly;in the aging peak stage(t= 32min),the number density of the precipitate reached the peak,and the size refinement was obvious.At this time,the precipitate was mainly spherical in shape;in the over-aging stage(t> 32min),the precipitate began to grow and coarsen at this time,with the aging With the extension of time,the size of the precipitate becomes larger,the number density decreases,and the shape gradually changes from spherical to ellipsoidal,short rod-shaped.The experimental statistical results show that the addition of Ni and Al elements can promote the nucleation of precipitates,increase the number density of precipitates and refine the size of the precipitates.In the same aging time,the size of the Cu-rich phase in the experimental steel with the addition of Ni and Al elements is always smaller than the size of the copper-rich phase in the experimental steel without adding any elements,indicating that the co-addition of nickel atoms and aluminum atoms reduces the Cu-rich phase Growth and coarsening rate.At the peak of aging,the precipitates in the steel always present a transitional Cu-rich metastable phase of BCC structure.