Influence of the SPD Processing Features on the Nanostructure and Properties of a Pure Niobium
The structurization of a high purity niobium from double electron-beam melted cast microstructure to fine-grained microstructure was completed by equal-channel angular pressing by the Bc route up to a Von Mieses strain of 13.8. In addition, for the viscoplastic behavior study as well as nanostructure and properties improving the hard cyclic viscoplastic deformation, die forging at room temperature and followed heat treatment with low heating rate were conducted. The nanostructure of processed samples was characterized by transmission electron microscopy and X-ray diffraction testing. This paper focuses on several new trends in the study of improved mechanical and physical properties of pure niobium, to what purpose these materials will be used in industry. The crystallite size, microstrains and dislocation density in severe plastic deformed pure niobium were calculated and electric conduction was measured. The nanocrystalline microstructure with minimal crystallite size down to 62 nm as mean in crosssection of sample was received. By this the dislocation density varies from 5.0 E+10 to 2.0 E+ll cm-2 and was maximal for pure niobium which has minimal electrical conductivity, maximal value of hkl-parameter and maximal relative microstresses. The microhardness was maximal for sample after 12 passes by Bc route and for samples with 8 and 10 passes followed heat treatment at 170 and 350℃. The mechanisms answerable for the electronic conduction were discussed according to the microstructure evolution in the different directions and for different strain levels.
L.Kommel V.Mikli R.Traksmaa M.Saarna A.Pokatilov S.Pikker I.Kommel
Department of Materials Engineering,Tallinn University of Technology,19086 Tallinn,Estonia Materials Research Center,Tallinn University of Technology,19086 Tallinn,Estonia Metrosert Ltd,Aru 10,10317 Tallinn,Estonia lnstitute of Physics,University of Tartu,Riia Str.142,Tartu 51014,Estonia Institute of Standards,Ozernaja Str.,46,Moscow,Russia
国际会议
5th International Conference on Nanomaterials by Severe Plastic Deformation(第五届剧烈塑性变形纳米材料国际会议)
南京
英文
785-790
2011-03-01（万方平台首次上网日期，不代表论文的发表时间）