Study On The Microstructure Control And Toughening Of High Deformation Zirconium

Zirconium is widely used in aerospace,military,nuclear,atomic,and medical fields due to its unique characteristics,but its mechanical properties directly limit the scope of application.Normally,the relationship between strength and plasticity of metal materials is inverted.breaking the limition of the inverse relationship between strength and plastic,is the scientific issue on which scientific researchers have been studying.In order to break through the limitation of the inverse relationship between the strength and the plasticity,to have high fracture toughness,high strength and plasticity of zirconium.In this paper,Zirconium sheet was subjected to strong plastic deformation by liquid nitrogen low temperature rolling and electroplastic rolling,the rolled samples were subjected to heat treatment and electrical pulse treatment.The effects of rolling method,rolling parameters and heat treatment conditions on the mechanical properties of zirconium metal were studied.The Zirconium sheets were subjected to strong plastic deformation by liquid nitrogen low temperature rolling.the samples were annealed 500°C for 1h,the samples were recrystallized.The size of the grains was 2-3?m and many Nano-defect structures were in the grains.This structure improves the fracture resistance of the sample.the tensile strength and failure elongation of the samples were 555 MPa,29.7%,respectively,and the fracture toughness reached 146MPa?m1/2,which showed high fracture ability and high strength plasticity.The Zirconium sheets were electroplastic rolled with different parameters such as pulse voltage,pulse frequency,pulse width and rolling line speed.The multi-scale structure compared with nanocrystalline,ultrafine and coarse crystal was prepared by annealing 450°C for 1h.The existence of multi-scale structure improved the work hardening ability of the sample.The tensile strength and failure elongation of Zr samples were 626 MPa,29.4% respectively,which showed high strength and plasticity.The Zirconium sheets were rolled through the meathod of liquid nitrogen low temperature rolling,producing a lot of defects.Tensile strength were 828 MPa,uniform elongation and failure elongation were 2.48% and 10.37% respectively.After 8V electric pulse treatment,there were a lot of nano-grains,and some large grains around the nano-grains.Tensile strength was 739 MPa,uniform elongation and failure elongation were 4.55% and 14.47%,showing good strength and plasticity.