Structural Stability Control And Mechanical Properties Of Gradient Supernano Ni Alloys

Gradient super-nano grain(GSG)metal materials have excellent strong-plastic matching and comprehensive mechanical properties,which have received extensive attention from many researchers.As one of the typical bottom-up methods for preparing GSG metal materials,the samples prepared by electrodeposition have high interfacial energy,which makes the super-nano grain structure of the surface layer unstable.;however,top-down preparation of GSG metal materials Methods,mainly various surface plastic deformation techniques,can obtain surfaces with lower grain boundary energy,but the sample size is severely limited.Therefore,how to prepare highly stable bulk GSG metals is the main research goal of this thesis.In order to achieve the above goals,this thesis adopts the combination of bottom-up and top-down techniques,and exploits the advantages of both to prepare bulk GSG Ni alloys with high corrosion resistance,high wear resistance and high stability.(1)The as-deposited GSG Ni-Mo alloy was prepared by electrodeposition technology,and relaxation annealing was used to reduce the interfacial energy of the sample to obtain the as-annealed GSG Ni-Mo alloy.They were subjected to microstructural characterization,hardness testing,electrochemical analysis,and friction and wear testing.The results show that the low temperature relaxation annealing has no obvious effect on the structure of the samples;the wear resistance and corrosion resistance of the as-annealed GSG Ni-Mo alloy are improved to a certain extent compared with the as-deposited NG and GSG Ni-Mo alloys.(2)The as-deposited GSG Ni-B alloy was prepared by electrodeposition technology,and a high content of butynediol was added during the deposition process to introduce a twin structure,and relaxation annealing was used to further reduce the grain boundary energy to prepare the as-annealed GSG Ni-B alloy,and they were subjected to microstructure characterization,hardness test,electrochemical analysis,friction and wear test and DSC analysis.The results show that the structure of GSG Ni-B alloy changes uniformly and there is no obvious interface;the corrosion resistance of the as-annealed GSG Ni-B alloy has a certain degree of improvement compared with that of as-deposited NG and GSG Ni-B alloy;during the friction process,the as-annealed GSG Ni-B alloy can maintain a low friction coefficient for a long time for wear,and the wear resistance is greatly improved;and the DSC data confirms that the grain boundary energy of the as-annealed GSG Ni-B alloy decreases.(3)The as-deposited GSG Ni-B and Ni-Mo alloys were prepared by electrodeposition technology,and the grain boundary energy was reduced by relaxation annealing,and then the low-energy interface was introduced by surface rolling treatment(SRT)technology to prepare as-annealed-modified GSG Ni-B and Ni-Mo alloys.For the analysis of surface hardness and thermal stability,the as-annealed-modified GSG Ni-B and Ni-Mo alloys have a certain degree of improvement compared with the corresponding as-deposited samples;the wear resistance of the as-annealed-modified GSG Ni-Mo alloy The properties and corrosion resistance are significantly higher than those of the as-deposited and as-deposited-modified GSG Ni-Mo alloys.In summary,GSG Ni-B and Ni-Mo alloys were prepared by electrodeposition in this paper,and relaxation annealing and surface plastic deformation were used to further improve the comprehensive mechanical properties,corrosion resistance and stability of the materials.The preparation of metal materials with high stability and excellent comprehensive mechanical properties provides theoretical basis and technical support.