Study On The Microstructure And Properties Of Copper Wire By Cryogenic Wire Drawing

Ultra-fine crystal copper has fine grain which showed high strength, electricalconductivity, thermal conductivity and other properties, thus has broad applicationprospects. while the process how to get a fine grain/superfine crystal and continuousproduction is still not realized which limits its application. The fine-grain/superfinecrystal microstructure of the copper wire was obtained by cryogenic wire drawing in thispaper, at the same time discusses the low temperature recrystallization annealingtreatment for a short period of time and different temperature recrystallization annealingprocess. On this basis, utilizing the analysis methods of optical microscopy, scan electronmicroscopy, conductivity testing and other mechanical properties testing, we havestudied the mechanical properties change in the drawing process of pure copper bydifferent treatment, the effect of cryogenic treatment on sample’s microstructure andmechanical properties after drawing or annealing, the effect of cumulative deformationon sample’s structure after annealing and the effect of annealing system on themicrostructure of materials by cryogenic drawing. The sample’s mechanic properties andconductivity were tested and analyzed in different annealing system. The results were asfollows:1).Compared to room temperature drawing deformation, the copper by cryogenicwire drawing has more high tensile strength, and with the increase of cryogenic time, thetensile strength has been increased all the time; while the elongation increased firstly andthen dropped with the cryogenic time increasing. The conductivity declined all the timewith the cryogenic time increasing.2) With the mold size decreasing (i.e., the increase of deformation), the tensilestrength increased sharply while the elongation and the conductivity declined. The mainreason is that the greater the deformation, the higher dislocation density and the smallergrains size was obtained which caused the defects increased quickly.3) The tensile strength declined firstly and then increased with the drawing rateincreasing, On the contrary the elongation and the electrical conductivity appearedincreased firstly and then dropped with the drawing rate increasing.4) Both annealing process all reduced the tensile strength and improved electricalconductivity. Drawing copper was treated by recrystallization annealing at200℃underdifferent time which could to control the grain size easierly and gains the smaller and uniform tissues; While drawing copper was treated by recrystallization annealing at2minutes under different temperatures obtained the coarse grain, and not easy to control.Low short-term recrystallization after cryogenic wire drawing technology has thepotential to fabricate pure copper with high strength and high plasticity and highelectrical conductivity.