Study On The Process,Microstructures And Properties Of Pure Ti(TA1)Ultrafine Wire Produced By Cold-drawing

The titanium and its alloys have been widely applied in aerospace,biomedicine and automotive due to the good properties such as light,high specific strength,corrosion-resistance,good performance in biocompatibility and nonmagnetic.Pure Ti wire has been paid more and more attention and it is feasible to produce φ0.1mm by drawing.It is useful for pure Ti wires with various diameter in some areas of biomedical,filtration,mariculture.However,the reports of ultrafine pure Ti wire(d<0.1mm)are less.Ultrafine pure Ti wires will be significant in some areas such as tissue repairing,fine filtering,porous materials.Meanwhile,the problems of poorly plastic deformation and sticking die easily during the manufacturing process of pure Ti wire make it difficult to produce ultrafine wires.In the present work,the process of high speed wire drawing and low speed wire drawing are researched to produce ultrafine pure Ti wires in diameter of 0.05mm from 0.1 mm.Finally,the φ0.046mm Ti wire is successfully produced by low speed cold-drawing.Then microstructures,mechanical properties and annealing process are studied by means of optical microscopy,scanning electron microscopy,room temperature tensile test and X-ray diffraction.The primary conclusions are as follows:The process of continuous wire drawing of TA1 ultrafine wire with high speed is difficult to achieve by using different moulds,lubricants and drawing speed.It is hard for Ti to adhere lubricants so that sticking die happens,easily during drawing because of severe friction and high temperature.Colloidal graphite is a useful lubricant and 10m/min is the effective drawing speed in low speed wire drawing process.The(φ0.046mm ultrafine pure Ti wire is successfully produced by low speed cold-drawing without medium annealing.The equiaxed microstructures were observed in φ0.1 mm TA1 wire.The microstructure is fine but inhomogeneous,and the average grain size is 3.0 μm.Most of grains were elongated along the drawing direction during cold-drawing and equiaxed microstructure turned into fibrous due to severely deformation.Dislocation slipping is the main mechanism of plastic deformation.The inhomogeneous microstructure in original wire caused non-uniform stress distribution and local stress concentration during deformation,which increased the strength and decreased elongation sharply from 16.4%to 2%after 14.99%reduction.With the increasing of cold-drawing reductions,the strength increased and elongation changed little.The yield strength and tensile strength of φ0.046mm TA1 ultrafine wire are 881MPa and 990MPa,respectively,increasing by 105%and 72%compared withφ0.1mm.At the same time,the stable<10(?)0>fiber texture was formed at little reduction,and then no more changed with further cold-drawing.The fine recrystallization structure of the φ0.046mm TA1 ultrafine wire was obtained after annealing treatment of 500℃/20min.The average grain size is 2.0μm.The yield strength,tensile strength and elongation are 520MPa,644MPa and 10.6%,respectively.The texture was still<1010>fiber texture after annealed at 500℃/20min.And it changed to<11(?)0>fiber texture at high temperature at which new grains grown.