Study On The Microstructure And Properties Of Nanocrystalline FeNiCo Alloy Prepared By Electrodeposition

FeNiCo Invar alloys were widely used in aerospace precision instruments and other fields due to its low expansion coefficient.Because of the excellent physical,chemical,and mechanical properties,nanocrystalline materials have attracted people's attention.If nanocrystalline FeNiCo alloys are available,which mechanical properties,thermal expansion,elastic modulus,and magnetic properties are worth studying.The electrodeposition method is one of suitable methods for preparing nanocrystalline materials,it has the characteristics of controllable grain size,simple equipment and low cost,but the abnormal co-deposition will appear during the iron-based alloys preparation,the preparation of FeNiCo ternary alloys by electrodeposition is a difficult problem.It is of great significance to prepare nanocrystalline FeNiCo alloy by electrodeposition method.Therefore,the preparation of nanocrystalline FeNiCo alloys by electrodeposition was explored,the effects of electrodeposition parameters and additives on the microstructure of FeNiCo alloys were studied,and the best process of electrodeposited nanocrystalline FeNiCo alloys was obtained.Then the thermal expansion,elastic modulus,hardness and magnetic properties of nanocrystalline FeNiCo alloys were investigated.Besides,the performance of heat treatment on the microstructure,thermal expansion,elastic modulus,hardness and magnetism of nanocrystalline FeNiCo alloy were explored.The research results are as follows:The best process parameters of electrodeposited nanocrystalline FeNiCo alloy:p H value 2,temperature is 40?,rotation speed is 20r/min,current density is 50 m A/cm²,duty cycle is 50%,frequency is 0.13KHz,electrode distance is 6cm,saccharin concentration is 2.0 g/L,BD concentration is 0.2g/L,Sodium dodecyl sulfonate concentration is 0.2 g/L.The nanocrystalline FeNiCo alloys with different compositions have been prepared by using the best electrodeposition process parameters.The grain size is 8-20nm,and the hardness of the alloy is about 395Hv.There is no phase transition characteristics in the resistance and DSC curves;With the increase of(Co+Ni)content,the thermal expansion coefficient of the alloy first decreases and then increases,the thermal expansion coefficient is the lowest when the content of(Co+Ni)is 36.23%,the thermal expansion coefficient is 4.27×10^-6/?,greater than the coefficient of thermal expansion of the coarse-grained Invar alloys.When austenite and martensite exist at the free surface and near the base surface,the modulus of the alloy remains unchanged within a certain temperature range.The nanocrystalline FeNiCo alloy is heat treated at 400?.With the increase of the holding time,the grains size increases and the hardness of the FeNiCo alloy decreases,and the coefficient of thermal expansion decreases.The thermal expansion coefficient of the nanocrystalline FeNiCo alloy after aging at 200?for 5 hours is 3.9×10^-7/?.Compared with the unchanged elastic modulus of the deposited nanocrystalline FeNiCo alloy in a certain temperature range,the elastic modulus of the alloy softened after heat treatment.